 Good evening guys, how are you? So here is our today's session. Today's topic is acid and bases. Okay, so in this we'll see a few theories based on acid and bases then we'll see some pH calculation, POH calculation, acid and base dissociation, molarity, molality all the concentrations. Okay, so I hope you all can hear me. If there is any issue in my voice or in surrounding noise, please let me know. Okay, good Shradha. Thank you. Good. So now I'm sharing my screen. I'll share the presentation here. So there are a few important things today what we have to do or on which we have to focus. See, there are a few questions based on equivalent mass, right? Where suppose you have any compound in which valencies are different of anion and cation. So how to calculate equivalent mass of those compounds that is important. Now then we have to see the relation in between molarity and normality. Okay, I think this I have discussed with few of the students but not with all. So we'll see that then we will see how to calculate concentration with the help of pH. Okay, so these are the more important topics here. Let's start. Yes, here is our today's topic, acid, bases and salt. So first of all we'll see some basic properties of acids and bases. As we all know very well that acids are sour in taste but salt, sorry, bases are bitter in taste, right? Another thing acid changes blue litmus paper to red. For this we have, we know one short form also, right? How? The first one is ABR and another is BRB. So we all have learned this BRB thing, right? Base turn red to blue. That means base turn red litmus paper to blue. Similarly for acid, ABR, acid turns blue litmus paper to red. After this, acid reacts with metal to give hydrogen gas and salts, right? To give hydrogen gas with carbonates and bicarbonates to give carbon dioxide. So any acid when it reacts with metal it releases hydrogen gas and when it reacts with bicarbonates and carbonates it releases carbon dioxide gas. Okay, now in the base, base they are soapy in touch. Okay, they are little slippery. They are soapy in touch. I have shown you the picture of NaOH in the glass, right? And another thing is what? Base are very, very delicacy. They quickly absorb moisture from the environment, okay? Okay, the examples are what? HCl, H2SO4, HNO3, CH3COH. In case of bases, the examples are NaOH, KOH, calcium hydroxide, ammonium hydroxide, right? See, Baccio, we have around 70 slides, okay? So I'll just try to do all these basic part, all these like properties and all those things very quickly because we have to pay attention on questions, numericals, right? So if you have any confusion just please unmute your mic and then you can ask. So here are some common acids we have HCl present in stomach, H2SO4 in car batteries, HNO3 in explosives, acetic acid in vinegar, carbonic acid in sodas and phosphoric acid in flavorings, in flavoring agents, okay? Some other acids like in orange lemon we know that there we have citric acid then in tamarind we have tartaric acid, tomatoes we have oxalic acid, these two are important, okay? Then in milk we have lactic acid, okay? In ant and bee string we have methanoic acid or formic acid. That is why we rub some, what should I say, that baking soda or some base when some bee sting or ant sting happens, right? Similarly some common bases we have sodium hydroxide, magnesium hydroxide, sodium hydroxide we use in soap and detergent or in drain cleaner, okay? If you might have seen there is one pouch comes like for drainage cleaner we all use in our household purpose, right? So the important content of that drainage cleaner is sodium hydroxide. Magnesium hydroxide will mostly use in antacid syrup, magnesium hydroxide, aluminum hydroxide these we use in antacid syrup, okay? Aluminium hydroxide is also useful in deodorants. Now the another component, another compound, ammonium hydroxide. Ammonium hydroxide we use in fertilizers in ammonia, okay? In the preparation of ammonia, okay? Next we'll see some chemical properties of acids and bases. Here we have few acids like hydrochloric acid, HNO3, H2SO4, how they react with any metal and liberates hydrogen gas. Now we have done test also for this, right? We have done these activities. How to know that gas is hydrogen gas and how to we know that a reaction is over? We can use a burning candle or burning candle in front of these gases. If it gives pop-up sound, that means this gas is hydrogen, right? So whenever any acid, any acid, whether it is strong acid or weak acid, see acetic acid is weak acid, HCl is very strong acid, whatever, whenever it will react with zinc it always releases, whenever it reacts with any metal it always releases hydrogen gas, okay? So it forms a salt plus hydrogen gas. So what is the pop test here? When a burning candle is brought near to the test tube containing hydrogen gas, it burns with pop sound, okay? This test is conducted for examination of presence of hydrogen gas. Early when base react with any metal it also produces salt and hydrogen gas. There is very common reaction where NOH reacts with sodium, NOH reacts with zinc and it produces sodium zincate plus hydrogen gas. Again the same pop test we can do to examine the gas. But all bases doesn't react with all kind of metals, okay? That is why such kind of reactions are not possible with all the metals. Now, action of acid with metal carbonates. When metal carbonates react with acid it produces carbon dioxide, okay? Carbon dioxide, salt and water. For example, Na2CO3 sodium carbonate, it reacts with HCl, it produces NaCl common salt and water and carbon dioxide, right? Similarly, sodium bicarbonate because again we have carbonate group, carbonate group always releases carbon dioxide after reaction with any acid or after reaction with water. So sodium bicarbonate reacts with hydrochloric acid to produce sodium chloride, carbon dioxide and water. Now there is a test for carbon dioxide gas. One test we have performed, one activity we have performed in our class that whenever you use burning sphincter or burning candle in front of this gas in the test tip or where this gas is releasing, it will work as a fire extinguisher, right? It extinguishes fire. So we can say that carbon dioxide gas is present. The test we have lime water test. This is also very common, right? When you use lime water, when you add lime water or when you just use lime water from which carbon dioxide gas is passing through, this lime water will convert into calcium carbonate and water. This calcium carbonate forms some white color precipitates or it makes the solution cloudy, okay? So when your lime water gets cloudy, you can say that there is carbon dioxide presence in your system. It passes excess amount of carbon dioxide for long time. The milkiness will disappear, okay? Because calcium hydrogen carbonate will form and this is soluble in water. So once our milky solution gets formed, we should remove that or if we will keep it there or if we will keep it in contact with carbon dioxide gas, what will happen? It will form calcium bicarbonate, see the formula C HCO3 twice, okay? C HCO3 twice. Why HCO3 twice? Because HCO3 has a valency 1, negative 1, okay? So many of you were confused in the valency of HCO3. So carbonate valency is 2 minus, CO3 valence is 2 minus but HCO3 bicarbonate valence is just 1 minus. So calcium bicarbonate formula will be CA HCO3 twice, okay? Because this forms and this is soluble in water, so milky appearance will disappear, milky milkiness will disappear. Next we have acid and bases they give neutralization reaction. We are very well aware of that, we are very well aware of it. Bees plus acid form salt and water, simple, very easy example we have NaOH reacts with HCl, it form NaCl and water, right? Now the reaction with metal oxide, reaction of acids with metal oxide, these reactions are important so please pay attention here. Metal oxide plus acid it will form salt and water, okay? Now for example copper oxide, copper oxide react with hydrochloric acid, it form COCl2 and water, okay? So whenever metal oxides react with acid it form salt and water. Why this happens? Because metal oxides are basic in nature, right? They are base or they are basic in nature, okay? Now in this reaction, you know one very important part or one very interesting part, copper oxide is metallic oxide, right? But when it reacts with hydrochloric acid it forms COCl2 that is blue green color compound, okay? So when this reaction proceeds it forms a blue green color layer or it forms a blue green color soluble salt, okay? Next reaction of non-metallic oxide with base, non-metallic oxides, non-metallic oxides means sodium oxide, calcium oxide, calcium hydroxide, magnesium oxides, right? Then they react with any base because again non-metallic oxides they have tendency to form acid after reacting with water, right? So they have acidic nature, okay? So carbon dioxide is non-metallic oxide, base is calcium hydroxide, it forms calcium carbonate and water. Again salt plus water because why the acid and bases are reacting because non-metallic acids are said to be acidic in nature. So that is why when they react with any base they form salt and water, okay? Now we'll do, we'll start doing some questions. These questions are pretty easy, okay? So write the word equation of following. The first question, dilute sulfuric acid reacts with zinc granules, dilute S2S4, this react with zinc granules and what will it form? ZNSO4 plus hydrogen gas, right? It's so easy, right? The next is dilute hydrochloric acid with magnesium ribbon, HCl, diluted HCl with magnesium ribbon Mg. What it will form? MgCl2, magnesium chloride. Why MgCl2? Because magnesium valence is 2 plus hydrogen gas. So to balance this equation I have to use 2 here. Now dilute sulfuric acid with aluminium powder. Sulfuric acid with aluminium powder. Now please pay attention here, okay? H2SO4 plus aluminium. Now we know that valence of SO4 is 2 minus and aluminium is 3 plus. So the formula will be, formula of salt will be Al2SO4 thrice, okay? Plus hydrogen gas. Aluminium sulphate Al2SO4 thrice and hydrogen gas, okay? So now we are done with this, okay? Another thing, give another question, give reason for following. Persons suffering from acidity are advised to drink cold milk. Tell me why, send me your answer in chat box. Very good Shraddha. Anybody else? Varsha, Tanmaya, very good Anand, good Adarsh. Okay, so basically what happens? Acid neutralizes by milk, okay? Milk is slightly basic in nature, good Shruti. So what should we write? Cold milk neutralizes acid in stomach, okay? Cold milk neutralizes acid in stomach. Now please listen to me carefully here. Yes, good Tanmaya. Please listen to me carefully here. Why we are asking to drink cold milk? Why not the normal milk? You know what? Milk pH is approximately 6.5 to 7 or 6.2 to 6.5, something like that, okay? So ideally normal milk is slightly acidic, okay? And with time acidity increases in milk, okay? But when you preserve it in refrigerator, its acidity doesn't increase, okay? So that is why cold milk is preferable when hyper acidity happens or when mouth ulceration happens, right? Okay, the next question. Soap is rubbed when stink of V and while vinegar is rubbed on stink of Vesps. So, okay, yes, correct. Okay, so why we rub soap because soap contains soap contains Vase, correct? And V is stink and and stings may what happens? They have, they release this mythanoic acid, they release mythanoic acid or formic acid, right? So to neutralize those effect of acids, we use soap. Soap has NaOH, right? Okay, but we use vinegar, vinegar in Vesps stink. Why? Because it has basic ingredients, okay? What are the compounds it contains? I'm just writing for your information, okay? I don't think it is part of your syllabus, but just for your general knowledge, you should know that. So it contains norepinephrine, the first content. Another one is hyalurodinase, hyaluronidase, sorry. Okay, the next and the last one is MCDP, mast cell degranulation peptide, okay? These three contain, these three chemicals, they are slightly, slightly basic in nature. Now I'm moving to another question, explained by farmer's spray, select lime on field. Very basic reason we all know that's right, to raise the pH of very acidic soil, right? Another thing, it also adds calcium to the soil, which itself is very vital, a nutrient for plants, right? Raghav, please put your mic on mute. Raghav, can you hear me? Please put your mic on mute. Okay, good. So the next question, a tarnished copper vessel being to shine again when rubbed with lemon. What is a tarnished copper vessel basically when some corrosion happens there, right? So what happened? Usually a layer of copper carbonate or copper hydroxide forms, that is usually green color layer, okay? So when we rub it with a lemon, this layer disappears. Why? Because this layer is basic in nature. Let's see the equation. When copper reacts with carbon dioxide, oxygen and water present in the environment, okay? It forms a layer of copper carbonate and copper hydroxide. This is a green color of layer and basic in nature. So when it reacts with citric acid present in lime, right? Or present in lemon. So what happens? This base react with acid and form salt. That salt is soluble in water and then it can wash out from with the help of water. See lemon is acidic. There's the rubbing of, rubbing the tarnished copper vessel with lemon. The basic copper oxide or copper carbonate react with acid present in lemon to form a salt, which is, which is washed away with water. Vashnavi, I think you have not connected your mic or your earphones. I cannot see your mic symbol here. Tanay, you also didn't connect your mic here. Shruti, you also, Shruti, sorry, Suthi, Siddharth, Shruti, Shaddhar, Shashwad, your mic is also not there. Okay, leave it. Next, what we have, why should, why should curd be not kept in copper or brass vessel? And what is done to protect it? So, you know what is very simple thing we have. Curd has a leptic acid, right? And it will react with copper or brass metal. As we know that the acids are having property to react with metal. So, leptic acid from the curd will react with copper and it form hydrogen gas and salt, right? When leptic acid react with copper, which salt they form, cuprid lectate. This is the, here is the formula we have. One second, guys, I have to go to the previous slide. Here we were talking about some citric acid, right? Yes, I'm just writing the citric acid formula. If you want to note it down, please. H8O7, okay? This is the formula of citric acid. So, we have curd and copper vessel. So, curd, we have leptic acid. It reacts with copper and it form cuprid lectate. That is why we should avoid curd in copper vessel. We should avoid to put curd in copper vessel or brass vessel. Now, what can we do? We can use steel container or glass container, okay? Some student, they answer me, ma'am, we can use plastic container also. Yeah, we can use, but I don't want to promote plastic. So, better to use steel and glass container, right? Okay. So, now, here I am writing the formula for leptic acid. C3H6O3. It's very simple. C3H6O3, okay? Okay. The next question, what we have. Why does stain of curry on white clothes become radish brown when the soap is scrubbed? On it, right? And turn yellow again when cloth is washed with plenty of water. Now, we all know very well that curry must have turmeric and turmeric is served as a indicator, right? So, turmeric remains yellow in acidic medium, but it turns into red in basic medium. So, whenever you rub some soap in your cloth, which is affected by turmeric color, what will happen? It will turn into red color, radish brown color. And because the high amount of water, it can remove soap from the cloth. So, again, that radish brown color will disappear and then it turned into yellow color. Guys, am I going very fast? Let's continue. Good. Thank you for your input. So, now we have next question. Tooth decay. Tooth decay start when the pH of mouth is lower than 5.5. Tooth enamel is made up of, oh, by mistake, I think wrongly I have written answer in the question. Okay, I will leave it. So, usually tooth decay starts when fine. So, what happens basically? The layer of teeth or the tooth are they are made up of calcium phosphate. It has the high constituent of calcium phosphate. This is very hard material, okay? Like water cannot wash it off or water cannot break it or any other solid what should I say? The food also, they also cannot break it. Now, what happens? Because calcium carbonate, it is basic in nature. Calcium phosphate, I'm sorry, calcium phosphate, this is basic in nature. So, when the pH of our mouth gets lower or pH of the mouth is lower than 5.5, slowly, slowly it removes this, removes this layer of calcium phosphate, okay? It neutralizes this layer and then remove it. So, what happens? That is why tooth decay happen, right? Now, the question is how the pH of mouth gets lower, right? How it can become lower? Explain why the pH in person's mouth becomes lower? The reason is what? Whenever we eat food, any kind of food, okay? It contains some amount of sugar. So, this sugar is convert into acid with the help of some bacterias. So, bacterias present in our mouth, they break down the sugar to form acid. This acid lowers the pH of mouth, okay? How the mouth pH become lower because of food and mainly because of sugar content of food, right? Okay, it's part of this question. What damage it causes or what kind of damage can happen? The very simple thing, tooth decay, right? Now, what values are conveyed by this passage? Raghu, please put your mic on mute. Thank you. Simple thing. What message or what value it conveyed? The simple thing that we should clean our mouth properly after every meal, right? To avoid formation of acid. Next, okay, this question is important. Baking powder is used in making certain food stuff like bread, cake, muffins and all, right? Whereas softness and fluffiness is required. What happens if your mother while baking cake forget to add baking soda? What will happen? Very simple thing, right? We all have learned that baking soda or baking powder, it releases carbon dioxide when we mix it with water or when we mix it with liquid in food like milk. So, what happens? The release is carbon dioxide and carbon dioxide causes fluffiness, right? So, if suppose we don't add baking soda or baking powder, what will happen? The cake or the food preparation will become hard, okay? And then the texture will also not very good. It is not chewable then. So, usually baking soda and baking powder act as a chemical liveners in cooking, okay? Causing them to rise spread slightly. Baking soda gives cookies a very chewy texture, coarse and just chewy texture and baking powder it makes light with fine texture, right? If you forget to add all these ingredients and what will happen? The food preparation, it will likely to be flat and hard, right? It happened to me once. I was preparing some cake or something but I forgot to add baking soda and even baking powder also and seriously it was it was very bad. Okay, now we will see some definitions of acids and bases. Again, I have to rush because still I didn't reach to normality and molarity part. So, the three theories what we have, the first theory we have Arrhenius theory, then Bronston-Lauri theory and then Lewis theory, okay? The Lewis name is important, Gilbert Lewis. He has published his theory in 1920. What are these theories? Arrhenius theory we know very well that Arrhenius says when any acid whenever it reacts with water it releases hydrogen ion and base whenever it reacts with water it releases OH-negative ion, okay? So, acid releases hydrogen ion but base releases OH-negative ion. So, Harshini, please put your mic on mute. Are you there? Harshini, are you there? Yes, ma'am. Please put your mic on mute. Yeah, thanks. So, acid releases hydrogen ion and base releases OH-negative ion. Now what is hydrogen ion? Hydrogen ion we know that it is H plus but it is hydrogen ion and it is hydrogen ion and it is very unstable. So, it reacts with it reacts with one water molecule and it converts into H3O positive. So, this comes from a base basically, this comes from an acid basically. So, we say that acid releases hydrogen ion and base releases OH-negative ion, okay? Now, both the situation can happen only in presence of aqueous solution, okay? Not everyone was happy with this theory. Why? That's very, very easy and very simple thing. What will happen with the compound which doesn't have any hydrogen or which doesn't has any OH-negative, right? So, to define those compounds other scientists and the scientists came in front, right? A major problem with Arrhenius definition of acid in basis is that it limits acid in basis to water only or just to aqueous solution, okay? Without water they cannot show their acidity their acidic and basic characteristics. Acid requires water to ionize and form hydronium ion. There can be no Arrhenius acid unless water is involved in the as a solvent, right? That's obvious, right? Then what happens? Bronstein-Dory theory came in front and he says acids are proton donor and bases are proton acceptor. Now it is not important that this reaction always will happen in aqueous medium or in water medium, okay? What is the important property of this theory? Acid are proton donor and bases are proton acceptor. How I have learned it? NH3, it converts into NH4 positive. It has accepted one proton and it is Bronstein-Dory base, okay? I have learned in this way. So, this might help you also and HCN, it donates H plus. So, this is proton donor. Acids are proton donor, right? See the reaction here, HF, this is one acid and H2O, when acid this releases H plus ion, it goes with water to form hydronium ion and fluoride ion, right? Now, after this theory, conjugate acid base concept comes. What is the meaning of conjugate acids and base? Conjugate acid and base, they are derived from or they are originated from the parent acid and base, okay? How? Suppose here we have acid 1 and base 1, okay? So, whatever we will have after the reaction, whatever acid and base we will have, we have to market 2-2, base 2, acid 2, right? So, if suppose you have first acid here, then base 2 will be conjugate base of this acid, okay? Like simply HA here we have, right? If hydrogen releases, we will have only A- A-. A-, this is a conjugate base of this acid. Why? Because it is originated from there, it is derived from there, right? Similarly, in base, H2O is serving as a purpose of base here, it accepts one proton. So, this is an conjugated acid, conjugate acid of this base, because it derives from or it is originated from this water molecule, okay? Now, how do you know that H3O positive and A negative is acid or base, right? As we have learned just now, that H plus, conjugate acid, acid donates H plus. This H3O positive has ability to donate one H plus ion, okay? That is why it is, it has a property like an acid. A plus, A minus, sorry, A minus, it can accept one proton, okay? It can accept one proton. That is why it has characters like a base according to Braunstein-Laury theory. Now, conjugate acid base pair, NH3 reacts with water to form ammonium and OH negative. So, NH3 is a base we know and then, because NH3 is a base, water will behave as an acid. NH3 convert into ammonia, ammonium ion, right? So, instead of writing 1, 1 and 2, 2, you can follow this also. Here it is base 1, here it is acid 1. So, NH3 convert to form ammonium ion, ammonium ion is a conjugate acid of NH3, okay? And OH negative is a conjugate base of water. Let's do these questions now. Identify the conjugate acid base pair in each equilibrium. The first, HSO4 negative reacts with water to form SO42 negative plus H3O positive. Now, how will you know that in the reactant portion which one is acid and which one is base? I will tell you this small thing here. See, water is converting into H3O positive, right? And I told you H3O positive, that means one extra proton, correct? Water has accepted one proton. So, water will be what? A base, correct? If water is base and then this H3O will be acid. So, can I write? Base 1, acid 1, okay? That means H3O positive is a conjugated acid of, conjugate acid of this water. Now, HSO4 negative, HSO4 negative is, it is converting into sulphate ion, SO42 negative. It is releasing hydrogen, right? Releasing hydrogen, tonating hydrogen, that means acid. So, here this is acid, acid 2. It forms SO42 negative base 2. Got it? So, sulphate ion is conjugate base of HSO4 negative and hydronium ion is conjugate acid for water. Now, the B part. C3H7NO2 react with hydronium ion. It forms water and this is this. Okay, fine. Hydronium ion, it releases one hydrogen ion to form water. So, H2O will be conjugate base of H3O positive, okay? And C3H8NO2 plus will be conjugate acid, acid of C3H7NO2, okay? Okay. So, Batu, I will share this worksheet with you. I think after this class also, you can solve all these easy questions, right? There are two questions based on conjugate acid and base. So, I will share this worksheet with you. You can solve by your own and if you have any confusion, just ping me. I will send you solutions as well. Actually, I just wanted to move on to some important questions, some important part of this topic. Okay, Varsha, do you have any doubt in this? Do you want me to do this? Here, Varsnavi, Varsha, and Aditi, Stuti, do you want me to do this here? Okay, Varsha, thanks. Stuti, Sharshwath, do you want me to do this here? Kushal, Harshini, Raghav, okay, great. Thank you. Okay, now we will see some relative strength of acid and their conjugate base. So, it's a very, very important thing to understand that whenever you are using a very strong acid and water, let's say, so whatever it will prepare, the base, conjugate base, definitely it will form a conjugate base. This conjugate base will be weak. Okay, this conjugate base will be weaker. Strong acid always produces conjugate, weak conjugate base and a strong base will always produce weak conjugate acid. Varsha for weak acid and weak base, okay? So, let's see here. Acid, very strong, the conjugate base will be very weak. If the acid is strong, base will be weak. Acid is weak, base will be strong, acid is very weak, base will be very strong. Okay? Why this thing happens? Because strong acid loses proton very readily. Okay? To form weak conjugate base. Weak acid do not lose proton very readily. So, it will form a strong conjugate base. Okay? Okay, next what we have, the pH of rain water. One question is there. pH of rain water from two cities, A and B was found, 6 and 5 respectively. The water of which city is more acidic? That's very obvious, right? B, right? Because B is 5. Now, find out the ratio, ratio of hydrogen ion concentration in this two rain water sample. Now, hydrogen ion concentration. Okay, what is this hydrogen ion concentration? pH is equal to minus log H plus ion, right? Now, we have to calculate hydrogen ion concentration. So, there is another formula we have. H plus is equal to 10 to the power minus pH, right? What is the pH of city A and city B? For city A, the pH is what? 6. So, can I say H plus ion concentration is equal to 10 to the power minus 6 and for B, H plus ion concentration is equal to 10 to the power minus 5, right? Now, we have to calculate the ratio of A and B. So, the ratio will be 1 is to 10, right? Ratio of A and B. What I did, I just divided A. So, I have 1 by 10 remaining, right? That is the ratio of A and B. Hope you all understood this. Any question, please unmute your mic. Very good. Shraddha, Adarsh, I have received your answer. They, very good. Okay. Students who are not sending me answers, who are not talking to me here. If you have any doubt, please unmute your mic and then ask, okay. Ananya, Aditi, then Druti, I didn't hear anything from you. Can I, okay? Okay, then. Next. Would you expect, what would you expect it should be actually? Here we have SNH2O tetra, 2 positive ion and hexa-aqua, 10. Okay. So, how will you say and how can you say which one is more acidic here? Which one is more acidic? SNH2O4 or SNH2O6 with 2 plus ion and 4 plus ion. Tell me. But you tell me, which one is more acidic? Very good. I have got the answer second one. Okay. Good. The second one is more acidic. Why the second one is more acidic actually? Because it has more, hey, you guys are answering the second one. Okay. So, second one is a, okay, this is the first one. Correct. Yes. Here the second one can lose proton easily. Okay. It has 6 water molecule with 4 plus ion. It can release a proton easily. Okay. In case of any confusion, any doubt, unmute your mic and then you can ask. Okay. I am moving to the next slide. Now we have M4-teric solvent or M4-teric solution. What does it mean? The M4-teric, that means, which can behave as an acid as well as an, as a base. Okay. Depends upon the situation. Now, H2SO4. H2SO4 is what? Is it M4-teric? No. Never. Because it always behaves as a strong acid. H2SO4 minus, yes. Why it can be M4-teric? Because it can accept one proton and it can form H2SO4. Right. Acceptance of proton leads to a character of a base. Okay. And as well as it can release one proton, it can release one proton to form SO4-2 negative. So, it can form SO4-2 negative. It can form H2SO4. Right. That is why it is, it is an M4-teric solvent. Next. SO4-2 negative. Can SO4-2 negative behave as an M4-teric? No. Never. Why? Because it doesn't have any proton to lose. Correct. It already has two extra electrons. It needs some proton. It cannot lose proton. Okay. Now, we have some conjugate acid and base pair. HF. What is the conjugate base of this? F minus. Okay. Now, SO4-2 negative. SO4-2 negative. What will be the conjugate acid of this? HSO4. Listen to me carefully. Okay. SO4-2 negative. If I say SO4-2 negative. What, this is a base. What is the conjugate acid of this? You have to add only one proton, HSO4-2. You cannot write H2SO4. Okay. Because sulphate ion first converts into HSO4-2 after that it converts into H2SO4. Okay. So, HSO4 or SO4-2 negative is a base. But when it gains one proton it converts into HSO4-2. This is M4-teric and this is the conjugate acid of your HSO4-2 negative. Now, ammonium ion. Ammonium ion has one positive charge. That means it has one extra proton. It can easily donate one proton. So, ammonium ion is an acid here. It forms NH3. This is the conjugate base of ammonium ion. Similarly, you can do it for water and hydronium ion. Right? Lewis theory. What is it actually? When an acid accepts a pair of electron, when an acid accepts a pair of electron, that chemical is known as acid. But a base donates a pair of electron. A base always donates a pair of electron. The best example for this I can tell you. Ammonia. Ammonia, you know that nitrogen has five electrons in outer shell, right? But out of these five electrons, what I was saying is, yeah, but out of those five electrons, three electrons only has been shared. I'm writing here. So, electrons has been shared with hydrogen. It has one lone pair of electron. Right? Now, what happens when hydrogen ion comes in contact with ammonia? Hydrogen ion. Okay? Hydrogen ion, that means what? Only proton. It doesn't have any electron. It takes one electron from this nitrogen of ammonia. Okay? Now, it has one electron. Then after this share, this nitrogen share this electron with hydrogen. Okay? Because nitrogen is previously nitrogen was donating one electron. That is why it has one positive charge. Because nitrogen has donated one electron. That is why it has positive charge. And then it shares another electron with hydrogen. That is how it is returned as NH4 positive. Now, because ammonia is donating one electron, it serves as a base. So, this is the Lewis base and constant Dory base also. Okay? But just give me a minute. Okay? So, now we are done with all these theories. Then we have some acid and base dissociation constant. Okay? Dissociation constant, basically, what does it mean? It is just the ability to dissociate or how much any acid has ability to dissociate. Right? How much it can dissociate? So, dissociation constant is just like the equilibrium equation, equilibrium expression. Right? The concentration of product divided by concentration of reactant. Right? So, here, when acetic acid dissociate to form hydronium ion and acetate ion, so the Ka, dissociation constant of acid or ionization constant of acid will be concentration of hydronium ion and acetate ion divided by concentration of an acid. Okay? Similar thing we have for base also. But base dissociation constant is denoted by Kb and acid dissociation constant is denoted by Ka. Now, please try to understand one thing. If you have higher Ka value, higher the Ka value, that means the strong acid. How can we say this? Because Ka value is depending upon the concentration of ions. If you have more concentration of ions, more Ka value, more Ka value, more acidic strength. Okay? So, acid and base ionization constant are measure of strength of acid and bases. Okay? Larger the Ka and Kb value, the larger the acid or base. Larger the Ka value. What does it mean? Stronger acid, more ions found in solution, more easily donate a proton. Okay? Weak acid, that means only ionized to a small extent, to a state of chemical equilibrium. As much as acid is dissociating, the ions are again forming in an acid. Right? We have seen one example of acidic acid dissociation in equilibrium class. See here, this is the formic acid. It dissociate into hydronium ion and formate ion. But it stabilize equilibrium as soon as possible. Why? Because it is very weak acid. It tries back to convert into acidic form. Okay? Now the important thing is what? Ionic product of water or ionization constant of water. It is denoted by Kw. I have told in class also, please write the symbol properly. It is Kw, ionic constant or ionic product of water. What is it? Kw is equal to H3O positive and OH negative. That's it. Okay? Because this is liquid, so we have to take it as a one. Now, what is the value of this? The value of this is H3O positive and OH negative, that is equals to 10 to the power minus 14 or 1 into 10 to the power minus 14. Okay? Now, let's compare all these three values. If you have H3O positive and OH negative in equal amount, your solution is neutral, like water. Okay? If you have H3O positive, hydronium ion is greater than hydroxide ion, this solution is basic. What's the matter? Everyone is sleeping in the class. Nobody is answering me. Nobody is opposing me. You should say that I am wrong. If the hydronium ion concentration is more than hydroxide ion, then your solution should be acidic. Guys, what are you doing? Is the class getting very bold? Still no participation. Okay, let's make it more interesting now. So, if your hydronium ion concentration is less than hydroxide ion concentration, then what? That means the solution is basic. Why basic? Because obviously, hydrogen ion concentration is more, right? So, what is the important thing in this slide? That H3O positive into OH negative concentration is equal to 1 into 10 to the power minus 14. Okay, learn this properly. We have to use this in calculations. Okay, now this, here we have pH strip. We are aware about the pH thing, right? So, I am going forward now. Okay, here we have some acidic strength of some liquids, what we use in household purpose, in our daily life routine. Okay, so what is important for us? 6.6 is the pH of cow milk. 7 is the pH of distilled water. 7.4. pH is the pH we have for blood. 6 pH we have for yogurt. Vinegar pH we have 2.4. Lime juice we have 2.3. And hydrochloric acid that is in stomach, the pH is 0.1. Okay, 12.4 we have pH for lime water. Okay, now we have some formulas. What are these formulas? I am highlighting it here. A pH is equal to minus log H plus and concentration. That means when the concentration of H plus and is given or when the concentration of your acid or base is given, you can calculate its pH. Similarly, the POH is minus log OH negative ion, right? And the H plus ion concentration, if we have to calculate, then 10 to the power minus pH similarly for OH negative. So, please write all these four formulas, five formulas, sorry. I know you all are aware of it, but still please write it. Okay, let's do some calculations now. Calculate the pH of following 0.02 molar HNO3, 0.05 NaOH and 0.02 H2O so forth, 0.01 molar of MGOH twice. So, I will share my screen again. I have shared my screen. Hope you all can see this. Okay, here is the first question, solution of the first question. We have to calculate the pH of 0.02 molar concentration of HNO3. How will we calculate? See, the concentration of HNO3 is what? 0.02. Can you say that 2 into 10 to the power minus 2, right? So, HNO3 releases one hydrogen ion, the one molecule releases one hydrogen ion. So, the same concentration of hydrogen ion we will have in the solution. H plus is equal to 2 into 10 to the power minus 2. Now, we will use pH formula. pH is equal to minus log H plus ion, right? So, we will put the values minus log base 10, H plus ion concentration is 2 into 10 to the power minus 2. Done? Now, here we have to use a product log, product log. Okay, what is it? Log base 10 M into N converts, convert into log M plus log N. Log M plus log N, okay? This happened just a minute. Yeah, log M plus log N. Okay, so now, this will convert into minus will come outside. Log 2 plus log 10 to the power minus 2. Okay? So, guys, I would suggest you to learn log values from log 2 to log 6. Okay? So, I am writing it here. Log 2 value is 0.3010. Instead of wasting your time to see log value in the log table, it is better to learn at least 3 or 4. Log 3 value is, this is all for a base 10. Okay? Please, 0.477. Log 4 value is 0.6020. Log 5 value is 0.689. I am writing it here, 0.6989. And then log 6 value is 0.778. So, there are few values you can learn. Now, here we have log 2. As we know that log 2 value is 0.3010. See, I can write it here, log 2 value. Now, what we have? Log 10 to the power minus 2. So, we know that one more formula, right? Log M to the power N is equal to N log M. So, this 2 will come in front. This 2 will come in front. It will be 2 log base 10 into 10. Okay? So, log base 10 into 10 will be 1. So, that is how you have 0. So, you have 0.3010 minus 2. And then the answer will be minus 1.699. Hope you all understood this. Any doubt? Any question? Message me. Good Ritu. Now, I want participation of everybody. Everybody. We have started important part. Now, you have to keep messaging me. Okay? Sanjana, I can't see your mic. You have not attached earphones. Kushal, you also. So, at least participate through chat box. Next question. 0.05 molar NaOH. Again, it's like the previous one. But instead of pH, we'll calculate PoH value. So, here the PoH value will be, first of all, the concentration will become 5 into 10 to the power minus 2. So, PoH value again will be like this. Log 10 5 into 10 to the power minus 2. Again, we will use this product rule. So, PoH is equal to minus log 5 value. What is the value for log 5? Log 5 is equal to 0.6999. So, I'll just directly put the value here. See. Excuse me, ma'am. Yes, Vita, tell me. Ma'am, like in our class like they taught us, we can't take the base like OH negative concentration just like that. Like you have to use that 10 to the power minus 14 derived the H plus concentration and then use it. We are using not 10 to the power 14 that 14 thing. pH plus PoH is equal to 14. Now we have calculated PoH. So, we can calculate pH with the help of this. Okay, ma'am. Means you are saying that from the beginning you cannot use, you cannot calculate PoH. Is that? No, like we haven't done anything like that. Like we converted everything into H plus and then did it. Okay. Okay. Let's try that process also. Here you have concentration of OH negative. So, H plus into OH negative is equal to 10 to the power minus 14. Right? Now you have concentration of OH here. H plus concentration. OH concentration is what? 5 into 10 to the power minus 2. 10 to the power minus 14. Okay. Now, H plus and concentration will be 10 to the power minus 14 divided by 5 into 10 to the power minus 2 minus 2 minus 14 minus 12. 1 by 5 will be 0.2. So, it will be 2 into 10 to the power 13. Am I right? Minus 13. This is the concentration of H plus ion. So, H plus ion concentration what we have got is 2 into 10 to the power minus minus minus minus 13. Right? Now, PoH is equal to minus law H plus ion concentration. Right? So, PoH is equal to minus log H plus ion. We have M into N rule again. Yes. Any doubt? Any question? Okay. No doubt. No question. I am going forward then. What I was saying is this is M and N rule again. So, log 2 plus log 10 to the power minus 13. PoH is equal to minus log 2 value is 0.3010. 3010 plus minus it will be minus 13. Minus 13 log based on 10. So, as we know that the whole thing this is the whole thing is equal to 1. So, PoH is equal to minus 0.3010 minus 13. So, PoH is equal to 12.6 minus 12.6 minus and minus will be plus. So, PoH is equal to 12.69. Okay. Is this way fine with all of you? Is this way better? Are you guys can hear me? Okay. Varsha. Good. Aditya. Good. Yes. They are good. Okay. So, basically what I was trying to say that if you have any base, right? If you have any base, so ideally I don't know what should be there but ideally what I prefer to always go through a base concentration PoH and then you calculate with the help of this PoH and this pH formula you calculate it. But it's okay. It is not done in your class and leave it. We will convert that OH ion concentration. This OH ion concentration code we will calculate H plus ion concentration first and then we will calculate pH itself. Okay. Hope this should be fine. Now I am moving to the next part of this question. Next part is the third part. We have to calculate the pH of 0.02 H2SO4. I forgot to write unit. 0.02 molar H2SO4. Please remember one thing that one molar H2SO4 will release two molar of H plus ion. So, here we have 0.02. So, 0.02 into 2 will be H plus ion. Okay. So, H plus ion concentration will be 4 into 10 to the power minus 2. Got it? If I put these values in the formula, pH is equal to minus log H plus value, what will happen? I will have log 4 plus log 10 to the power minus 2. Okay. As I have told you, log 4's value is 0.6020 minus log 10 to the power minus 2. So, minus will come in front, minus 2 will come in front and log best 10 into 10 will be 1. Log 10 best 10 will be 1. Okay. So, this will become 1. Now, 0.6020 minus 2 will be equal to 1.4. Minus 1.4 will be there and then minus minus will become plus. The pH is 1.4. Okay. But so, am I going very fast? Should I reduce my speed? Anand, Aryan. Okay. Good. Good harsh name. Sanjana, Anand, Kushal, Dhrutti, Aditi. Where are you guys? Okay. The next question we have, the last part of this question, 0.01 magnesium hydroxide. Again, the same logic is applicable. Magnesium hydroxide, that means 2H, OH negative ion. So, whatever the concentration is given, you have to multiply it by 2. Why? Because it is releasing 2H plus ion. Right? So, whatever the concentration you have, it will release twice of the amount of those concentration. So, the concentration of OH negative will be 0.02. Right? Or you can say 10 to the power minus 2. Again, because I think I went through POH thing, I will just go with another way. Okay. OH ion concentration is equal to 10 to the power minus 14 divided by H plus ion concentration. What I have? 10 to the power minus 2 here, this one. Okay. So, this will be 10 to the power minus 12. Correct? Okay. Now, H plus ion concentration, I have got it. H plus minus concentration, I have got it. This is 10 to the power minus 12. pH curve formula. Again, we will use here, pH minus log, H plus ion concentration. pH is equal to minus log. H plus is 10 to the power minus 12, base 10. pH is equal to plus 12. Yeah. That's it. pH is 12. Right? Hope you are fine with it. Okay. The next question. The next question is here. Ayo, what happened? Okay. Now, we have to calculate the following. pH of 0.5, 0.05 molar barium hydroxide and POH of 0.01 molar of HCl. These two questions are the similar one, what we have done till now. You guys have to try by your own. In case of any doubt, any question, ping me, I will share answers with you. Okay. Now, I am moving to the next question. Calculate the mass of NaOH that must be dissolved per liter of solution to get a pH value is 13. Okay. Now, what we have to do? We have pH value. We have to calculate mass of NaOH. Okay. From the pH value. Let's see how will we do it? I have done the mistake in this. Calculate the, this is fine. Here it is. Correct. The pH value of the NaOH solution is given. Okay. We have to calculate its mass. So, before calculating mass, we must be knowing the concentration. Guys, please remember, the concentration is always, should be calculated in molarity or molar form. Okay. Mole per liter form. Okay. So, pH, whenever we use pH formula, the H plus ion concentration, OH negative ion concentration, whatever concentration is given, that should be in molar only if it is related to pH. Fine. So, pH is equal to minus log H plus ion. Now, we have to calculate H plus ion concentration. Right? But I have given the pH is 13. So, H plus ion is equal to 10 to the power minus pH. This is another formula of H plus ion. Right? What I am doing, I am just directly putting the value. 10 to the power minus 13. Right? So, here, see here I have got the concentration of H plus ion. Right? The concentration of H plus ion, I have 10 to the power minus 13. Now, what are they asking? They are asking the mass of NaOH. So, to calculate mass of NaOH, we have to calculate. So, for this, we need concentration. We need concentration of NaOH. Okay? So, how do we calculate the concentration of NaOH? See here, H plus ion into OH ion is equal to 10 to the power minus 14. Right? With the help of this, we will calculate the concentration of NaOH. Because H plus ion, we have 10 to the power minus 13. So, OH is equal to 10 to the power minus 1. Now, what does it mean? 10 to the power minus 1 is equal to 0.1 molar. Right? The concentration of NaOH solution is 0.01 molar. Now, molarity is equal to mass per DM cube divided by molar mass. Okay? Now, mass per DM cube divided by molar mass is equal to molarity. So, we have what? 0.1 is equal to mass per DM cube divided by molar mass. How much is the molar mass for NaOH? I guess it is 40. So, can I do like this? Into 40. That is equals to mass per DM cube. So, this will be 4.0. Right? 4.0 gram will be important or will be dissolved in 1 liter to make the solution pH 13. Okay? Did you understand how I have calculated this? Aayu, what happened? 10 to the power minus 2. This is Shruti, previous question. Shruti, Harshini, Shraddha, please unmute your mic and please tell me what are you discussing. I didn't understand. Oh, okay. Okay. So, okay. Okay, then fine. I think I missed it. Ma'am, Shruti says her screen went off. Okay. I will stop sharing and I will share it again. I will stop sharing. I have stopped sharing the screen. Okay? Now, I am sharing it again. Guys, I have shared it again. Shruti, can you see this screen? Now, is it visible? Okay. Now, I am moving on to next question. Calculate the mass of calcium hydroxide. Calculate the mass of calcium hydroxide must be dissolved per liter of solution. The pH is 11. Okay? Now, we have to calculate the mass of calcium hydroxide. Please pay attention. It is little tricky. Okay. We know the pH is 11. Concentration of CaOH twice, we have to calculate. Right? The concentration of CaOH twice, we have to calculate. Now, how will we calculate? We have pH. So, first of all, H plus ion is equal to 10 to the power minus pH. This is the formula we are going to use. pH value I have placed here, 10 to the power minus 11. Now, I have the concentration of this H plus ion. What is the concentration? 10 to the power minus 11. Another formula we will use, H plus ion concentration multiplied by OH ion concentration is equal to 10 to the power minus 14. Right? So, we use the values. OH negative ion concentration is equal to 10 to the power minus 14 divided by 10 to the power minus 11. So, you will have 10 to the power minus 3. Now, you have got OH negative concentration 10 to the power minus 3. That is equals to 0.001 molar. Right? Okay. As I have told you, one calcium hydroxide molecule will release 2 OH ion. That means what? You have doubled the concentration of OH negative. Correct? OH negative ion concentration is doubled. Right? So, here if we have to calculate the concentration of solution, the compound itself, calcium hydroxide, what we have to do? We have to divide it by the concentration of OH negative ion divided by the 2. Right? So, the answer will be 0.005. Is it correct? 0.001 divided by 2. It should be 0.005. Sorry. Okay? The answer is 0.005. Okay? Yeah. This is correct. If you want to note it down, you can do. Otherwise, I will do one thing. This is the question and I will share all the questions as an worksheet. Okay? And I will share this PDF also. The thing, the whiteboard PDF also is available. I will share this both the things. But so, everybody unmute your mic. All of you unmute your mic. Dhruti, we have to find mass. Then only we will be able to find mass. This is the mass also. Till now, I just have to calculate the concentration. Okay? Okay. Now, who has? I told unmute your mic. You guys are not doing it. Yes, Radha. Aditi is there. Dave is there. Anand. No, Anand, there are not. This is two division classes. What we have done? I have all the questions in PPT and I was solving in front of you in the PPT itself. Right? But now what I have done, because in the accident basis, I have more number of questions. I have approximately 30 questions. So, I solved it in a PDF format in a whiteboard and then I was just explaining. What I'm finding out is here, you people showing your interest into this. Is it? Okay. So, is this way fine with you? Can we go ahead with this? Or you want to do something else? Yes, it's fine. Okay. Okay. Then great. Who has one student was there? Sushant. Sushant is not there today. Okay. Everybody now mute your mic. We will go back to the topic now. So, we have to calculate mass of calcium hydroxide. Okay. Till now, we just have calculated concentration. Thanks, Sruti. Actually, I also forgot that we have to calculate mass. Okay. I just calculated the concentration and then I announced this is our answer. Okay. And see, I don't have space also to calculate mass. I'll add one more slide here. So, the concentration of CA OH twice, we have got 0.0005 molar. We have to calculate mass. So, molarity is equal to mass by Tm cube divided by, divided by what? Divided by what? Divided by molar mass. Molar mass. Don't worry, it happens. So, molarity is equal to what? 0.0005 is equal to mass by Tm cube divided by molar mass of calcium hydroxide. So, it is molar mass of calcium hydroxide is this plus this, 74. Yeah. 74. Okay. Okay. So, 0.0005 into 74 that is equal to mass per liter. So, liter I am using one here as it is per liter only. So, this is 0.037 gram. Isn't it too less? Let me just check it out again. Okay. The concentration is also very, very less now. It's 0.0005, yeah, correct. Then mass should be very less. Then we have to calculate. We should calculate in laboratory in milligram. Okay. 0.037 gram of calcium hydroxide we need CA OH twice. We need, okay, to prepare the solution which has pH 11. Okay. Next question what we have? Now I'm moving to the slide. Next question we have calculate hydronium ion concentration of a solution having pH values 10.6. Kids, I am thinking that this question is from your textbook itself. You have this question in your textbook. Okay. So, you can just refer that. I have sent answers of all the questions but still have doubt. I will do that. Okay. This is the same question I think in your textbook. Here you have to take antilog of minus 10.6 or something like that. Okay. Now next what we have? Molarity, normality and molality. So, molarity what is the formula? Mole per liter or mole per DMQ divided by, sorry, mole per liter or mass per DMQ divided by molar mass. Right? Similarly, normality mass per DMQ, mass per DMQ divided by equivalent mass. Right? Then we have molality. Molality is not there for this year but because we have done so I am just doing it here. It is instead of mole per DMQ it is mass per kg, mass per kg of solvent. Sorry, I forgot to write. I cannot write it here I guess. You please write here. One minute. Just a second. Hello. Okay. Now the next question we have. Next slide we have percentage by percentage of, what I am saying? Percentage weight by weight. Okay. Percentage of solute weight by weight or amount of solute percentage of solute weight by weight, weight by volume and volume by volume. These calculations you might have done in ninth grade I guess. Okay. See the first question based on this. What is the concentration in percent weight by volume of a solution containing 39.2 gram of potassium nitrate in 177 ml of solution. Okay. See the amount of potassium nitrate is given in weight gram 39.2 and the volume is given in ml 177. Right? How to calculate this? We have a formula that percentage weight by volume is equal to mass of solute given divided by volume of solution given in 200. Why? Because we are calculating percentage. So the answer will be 22.1 percent. Okay. The next problem is similar to this. Here we have what is the concentration percentage volume by volume. See here both the things are given in volume solution containing 3.2 liter of ethanol in 6.5 liter of solution. Okay. So again 3.2 divided by 6.5 into 100. Right? We will have 49 percent volume by volume concentration of solute. What volume of what volume of 1.85 percent weight by volume solution is needed to provide 5.7 gram of solute. Now we have to convert the formula. Right? Here we have percentage value and we have to calculate volume. Right? So we will change this complete equation in the way of volume. Volume of solution is equal to weight of solute divided by, divided by a percentage thing into 100. Okay. So the answer will be 3.10 ml of solution. Any doubt in this? No question. Okay. I am moving to the another question. Calculate the mass of anhydrous copper sulfate required to prepare 400 centimeter cube of desi molar solution. Before doing this question, I have to tell you desi molar thing, centimolar thing and all. Okay. See here. Mass of the anhydrous copper sulfate is given. Sorry. Sorry. Sorry. Sorry. Mass we have to calculate. Volume is given and desi molar. That means concentration is given. What does it mean? Desi molar that means 1 by 10. Okay? 1 by 10 or you can say 10 to the power minus 1 or you can say 0.1 molar. Correct? Centimolar. Centimolar is 1 by 100. So you can say 0.01 molar. Correct? 10 to the power minus 2 or 0.01. Millimolar 1 by 1000. That means 0.001 molar concentration. Micro molar means 10 to the power minus 6 or 0.000001. Okay. So this is how centimolar desi molar and millimolar thing works. Now we have to calculate mass, this mass, mass of copper sulfate, anhydrous copper sulfate. Okay. Here I should have written molar mass. Molar mass of anhydrous copper sulfate is 39.41. Okay. And what is the mass? What is the mass required to prepare 400 centimeter cube of desi molar solution? So first of all we will see the desi molar solution. That means the molarity is given. One molar. Okay. Molarity is equal to mass per DM cube divided by molar mass. Now what are the things we have? We have molarity. We have volume. We have molar mass. Correct? Let us calculate this. Mass per DM cube is equal to molarity into molar mass. Yes, we can do that. 0.1 into 39.41. That is equals to mass per DM cube. Right? Now mass per DM cube is equal to 3.941 gram. Okay. But this is for one DM cube. Okay. Now we have to calculate it for 0.4. What I have to do? Should I write it here? Mass per DM cube is equal to 3.94 gram. Right? As I have told you that volume is given. What is the volume given? Mass divided by volume was given is 400 centimeter cube. So now I am converting it to decimeter. So I have written here 0.4. 0.4 decimeter cube is equal to 3.94. Now mass is equal to 3.94 into 0.4. Right? See we have came here. So the weight we have got this 1.58 gram required of what? CuSO4. That is it. CuSO4. Right? Next what we have? 1.26 gram of oxalic acid crystal are dissolved in 250 centimeter cube of solution. Calculate its molarity. It is very, very easy. Molarity to you guys can calculate very easily. Am I right? Okay. Let us do this. 1.26 gram of oxalic acid. 1.26 gram that means the mass is given. Dissolved in 500 centimeter cube that means what? Volume is also given. You have to calculate molarity or normality. I have written molarity but I have calculated normality. Okay. A big mistake I have done. Maybe the question is wrong or maybe I have written it wrong. Okay. Let us calculate its normality then. Doesn't matter. Okay. Okay. I remember that. Actually it is normality only. I have given the wrong question over there. Normality is equal to again mass by dm cube divided by equivalent mass. Divided by what? Equivalent mass. So how will you calculate equivalent mass? Equivalent mass will be that equivalent mass is equal to molar mass divided by valency. Valency. Right? What? Divided by valency. What is it? How will you calculate it? Equivalent mass is equal to molar mass. What is the molar mass of oxalic acid? Oxalic acid here is the formula I have written. The molar mass of oxalic acid is 126. So 126 divided by its valency. Oxalic acid valency is 2. So its equivalent mass became 63. Okay. Let us put the value here. Equivalent mass is 63. Now what is the mass given? Mass given is 1.26. Volume dm cube. How much it is given? 500 centimeter cube. So you can say that 0.5 decimeter cube. So mass per dm cube you have calculated 2.52. How? Mass is equal to 1.26 divided by 0.5. That is equal to 2.25. Equivalent mass also we have calculated 63. Now we just have to substitute all this value in the formula. N is equal to mass per dm cube divided by equivalent mass. 2.52 divided by 63. That is equal to 0.04 normal. So the normality of the solution is 0.04. Right? Next question we have. Calculate the mass of N-hydro sodium carbonate required to prepare 200 centimeter cube of 0.4 normal solution. This question is again given in your textbook. I feel that I have done it earlier also. Okay. So here normality is given. Okay. See the normality is given. Just one minute, one minute. So here we have another question. Normality is given. Volume is given. And equivalent mass we can calculate. So volume is what? 200 centimeter cube I have converted into 0.2. Equivalent mass of sodium bicarbonate. Sodium bicarbonate molecular mass is 60106. Sorry 106. And its valency is 2. So the mass is 53 gram. Now we can calculate normality. Mass per dm cube is equal to normality. Into equivalent mass I just have to rewrite the formula in in the form of mass per dm cube. Right? I have rearranged the formula actually. Mass per dm cube is equal to 0.4 into 53. Normality into equivalent mass. Right? So I have got 21.1. Now this is for what? This is for 1 meter. 21.1. Right? We just have to substitute the value of dm cube also. Right? Volume of value we have to put. So 22.1 22.1 into 0.02. So we will have 4.24. That is the gram mass for sodium bicarbonate Na2CO3 required to prepare 0.04 normal solution of 200 centimeter cube. Hope you all are understanding this. Okay? The next question. Calculate the normality of 0.06 molar solution of H2SO4. There is very small and simple relationship in between normality and molarity. Normality is equal to valency into molarity. Okay? So because H2SO4 we know the valency of H2SO4 or the basicity of H2SO4 is 2. Right? So 0.06 into 2 that is equals to normality. And the answer is 0.12. I am moving to the next question now. Okay. Next is calculate the amount of sulphuric acid present in 0. Sorry, present in 400 centimeter cube of what is it? 0.1 molar solution of sulphuric acid and 0.1 normal solution of sulphuric acid. Right? So first of all what we have to do? We have to calculate amount. Right? Amount we have to calculate. Well, molarity is 0.1 given and when normality is also given. Molarity is 0.1. Volume is 0.4 dm cube. So mass per dm cube now instead of dm cube I have kept the values. I have put the value 0.4 is equal to molarity that is 0.1 into molar mass. Molar mass of H2SO4 is what? 98. So with the help of this you can calculate mass is equal to 6.1 sorry 0.1 into 98 into 0.4 that is equal to 3.92 gram when molarity is 0.1. Okay. The next be part of this question. What will be the amount? What will be the amount of sulphuric acid when normality is 0.1? Volume is same okay the amount we have to calculate. Same thing mass per dm cube is equal to normality into equivalent mass. We have rearranged the normality of formula. Okay. What is the formula? Normality is equal to mass per dm cube divided by equivalent mass. So we just have rearranged the formula. Mass divided by 0.4 0.4 is equal to 0.1 into 49. Okay. The mass is equal to 0.1 into 49 into 0.4. So the calculation will be 1.96 gram when the normality is 0.1. 0.53 I will do it later. It is not so important. One point this also I will do it later. What question I was thinking to tell you in a minute? Yes. See come to this question. Calculate the mass of calcium phosphate required to prepare 200 centimeter cube of 0.4 normal of solution. Okay. This question is little tricky. Why it is tricky? I will tell you. Normality of solution is given 0.4. Volume is given 0.2. Molar mass we can calculate calcium phosphate. Molar mass is 310. Equivalent mass we have to calculate why? Because we have to calculate mass and in the formula we have equivalent mass we have to use it. Now what is the equivalent mass of calcium phosphate? Equivalent mass usually the formula is what? The formula is what? Molar mass. Molar mass divided by valency. But calcium phosphate now you have different different valencies here. Here we have different different valencies CA3PO4 twice. Okay this phosphate is 3 minus calcium is 2 plus. Ma'am like you've written in the sentence anion is SO4 to minus. Like where is SO4 to minus? Sorry sorry sorry sorry sorry my mistake. Actually I was thinking to do with another question. Aluminium sulphate that is the next question. So I just mixed it up as PO4 3 minus okay PO4 3 minus. Now what I was saying is different different valencies. So which valency you will use in the formula? That is a question right? What we have to use for these calcium phosphate anion sorry cation is CA2 plus and anion is PO4 3 minus. So the total charge on anion or cation is 3 into 2. How 3 into 2? See here CA3PO4 twice. Okay so calcium is what? 2 plus. But total 3 calcium you have to you have to multiply this charge. See CA2 plus and again CA2 plus. So total how many charges you have? How many cations you have? 3 CA2 plus. Am I right? So can you see that the total charge is 3 into 2 6? Similar thing is applicable for PO4 minus also. PO4 minus 2 minus you have. But 2 PO4 you have available here. 3 minus okay. So again it is 3 into 2 got it? So total charge of anion or cation whatever anything. Anything is fine is 6. What do you have to do? Equivalent mass is equal to molar mass 310 divided by 6 total charge total charge of anion or cation. Okay so 310 is equal to 51 but 310 divided by 6 is equal to 51.6. That is this is your equivalent mass. We just have to put equivalent mass here. So 0.4 normal solution is equal to mass divided by volume 0.2 divided by equivalent mass 51.6. So you have mass 4.1 gram. Similar question we have for aluminium sulphate. Okay again in aluminium sulphate how will you calculate equivalent mass? The equivalent mass calculate karne kele we have to use molar mass divided by its complete valency. Molar mass of aluminium sulphate is molar mass of aluminium sulphate. Yes I am writing here 342. Okay divided by its valency. Now again valency thing comes Al3 plus but you have 2 aluminium and 3 sulphate ion 2 minus. So again the charges will be the charge on anion or cation again it is 3 into 2 total is 6. Okay this should be divided by 6. Now the answer came 57 gram. It is 57.01 something so it is 57 gram okay. Okay so 0.2 is the normality mass we have to calculate 0.4 is the volume and 57 is equivalent mass. So mass we have calculated is 4.57 gram. Okay hope you all understood this. Okay beta chalo bye take care.