 Hello guys, good afternoon guys, please type in your name in the comment box. Okay, so Today in this session we are again going to discuss the question the chemistry board level question Okay, 12th board level question. Hello, Suresh. How are you? Is the question number 30? Hello, Suresh. Hello Sai Prena question number 30 solve this question What type of deviation is shown by a mixture of ethanol and acetone? Deviation is shown by the mixture of ethanol and acetone Positive deviation. Why it is positive deviation? It is positive deviation. Positive deviation is the right answer Just a second Speaking I'm getting Yeah, yeah Ma'am, can you ma'am? I am actually in between in the middle of something. Can you call me tomorrow? No, no It's not the same location. Yeah, it's in diagonal, but not the same location. Sure. Sure Okay, sorry guys Okay, so the answer of this question is positive deviation, right? Now you see why it is positive deviation because both ethanol and acetone are non-polar compounds. Okay Yeah, right AB forces are weaker than A and B forces, right? So this that's the basic thing of your positive or negative deviation that we have already discussed in the class Okay, both both compounds whether it is ethanol or Acetone you see here ethanol and acetone both are non-polar compounds non-polar compounds So now in this what happens the force of attraction Decreases here right. I'll write down in short here Force of attraction decreases here means like we have a a molecule Interaction interacting with BB molecule So we have two types of interaction a ABB and then when these two interacts will have AB interaction also Right, so one possibility is what this AB interaction is weaker than this a and B B interaction and this AB interaction is More than a or B B interaction, right? So an AB interaction is more than a or B B interaction. It is negative deviation Right when AB interaction is less than a or B B interaction. Is it it is positive deviation, right? And when it is exactly equal it is there is no deviation and then then the solution is exactly ideal solution, right? So here what happens the force of attraction decreases means interaction a B interaction is weaker than to that of a and B B interaction And that is why both shows are negative or sorry positive deviation, right? The answer is positive deviation Both are non-polar compounds What is the answer the second one a solution of glucose this is water labeled as this person by mass What would be the molality and molarity of the solution density of the solution is given? Tell me the answer question number B 30 B Molarity is 0.66. What about molality resist? Molality is 7.4 10 to a minus. I don't think it's correct. We just check your answer What what does tell me the answer? Are you still trying or should I solve it? Okay, right point six one is molality Yeah, it's correct point six one is correct This question you can do it easily just you need to know the formula of molarity and molality Okay, first of all you see Yeah, 10 percent by mass right means what if we take solute or suppose solution if it is 100 gram Then in this the solute the amount of solute present here is 10 gram This is what the meaning of 10 percent by mass, okay now Molarity formula if you write It is You must remember I have given you this formula it is percentage mass Into Density right percent is mass into density density Into 10 divided by Molecular mass of solute this is what the formula we have this formula. I have given you in Solution chapter itself. We have other formula also which is number of moles By Volume of solution This is what the formula we have so with both formula you can solve this question Okay, since the percentage mass is given you can use this formula also directly you will get the answer Okay, so you see here number of moles. Can you find out suppose if this is the No, the data given and we assume this so now we have solute 10 gram 10 divided by molecular mass of glucose That is nothing but the solute Gives you the number of most this number of most you can find out 10 by 180 Volume of solution is what density of solution is given Mass of solution we have assumed only the density and mass you have you can find out the volume of solution also You'll substitute it here. You'll get molarity This is the one way and most of you I think all of you know this formula easily, right? This formula you must have this information This formula usually we don't use for molarity But in solution chapter like if you remember I have suggested you to memorize these formula in terms of percentage mass So if you use this formula, you also get the answer regularly percentage mass is given that is 10 Into density is 1.2 Right, you have to take care of unit here. Don't forget that into 10 divided by molar mass of solute is what quantity So when you solve this you'll get the answer as 0.66 molar Right directly with this formula Okay, this formula you need to assume this solute and solution And then find out the volume of solution moles substitute here. You'll get the answer now molality is what? The formula of morality It is again number of moles Divided by mass of solvent mass of solvent And if this mass is in gram, then we have to multiply here by thousand right So what we can write number of moles will be 10 divided by 180 number of moles into mass of solvent is what 100 gram solution 10 gram solvent solute So solvent is what 100 minus 10, which is 90 in 2000 This is what you need to solve Right, which is 0.617 molar Very direct question is straightforward formula best question it is I hope you all understand this So this formula for molality you must remember very helpful in this particular chapter solution Percentage mass into density into 10 by molecular mass of solute We can also derive this with the help of this formula. It actually comes from this only Right, but when you memorize this formula you can directly use the data and get the answer Okay, so the first part of this question we'll see now Sorry Oh, yeah solve this one Definition of morality you let it be not required What is molal elevation constant kb this you already know Number of moles by volumes of solution in liter What is molal elevation constant kb? It is the elevation in freezing point. Is it freezing point? Elevation in boiling point of a solution when it's morality is one Yeah, it's correct kb is the Elevation in boiling point Of a solution Of a solution of unit molality Right, you can also write down the unit of kb also here. That is also you can do It should be elevation in boiling point when kf you write then it will be a little bit depression in freezing point Right, not elevation depression in freezing point. Anyways question number b 30 b. What is the answer? 47.5 Gram per liter What is the answer others tell me This is getting 47.5 Solution containing 15 gram urea multiple masses given per liter of a solution in water Has the same osmotic pressure A solution of glucose masses this in water to calculate the mass of glucose present in One liter of its solution all of you are getting 47.5 So We have a solution of urea Urea and water and then glucose in water Right, so when the solution is isotonic. So what we'll do we'll equate the osmotic pressure. So what we can say Both solution Both solution has Same osmotic or equal osmotic pressure So we can write pi one for first solution is equals to pi two For second solution and pi one pi two we know it is equals to crt. So we can write concentration c1 Is equals to concentration c2 Right concentration of the first one is what mole per liter So for urea it is 15 gram divided by 60 And solution volume is what one liter Is equals to for this mass we have to find out divided by 180 divided by one So when you solve this you will get m is equals to 45 directly. I'm getting 45. How do you get 47.5 all of you gram per liter This is the answer I'm getting Is it okay? It's given 190. Okay fine. I thought its glucose would be 180 Correct. So if you take 190 accordingly, then I think probably you will get the right answer 47.5 Anyways, so method is this only right so with 180 if it is This is the answer Right, I think here is the printing mistake because since it is mentioned glucose glucose molecular mass is 180 only Okay, so here is the printing mistake. We have anyways, so whatever molecular mass we have we'll take here. We'll get the answer accordingly correct Next question you see Do this cl cs2 c over stronger acid than this correct Yeah, right, which is probably correct. Second one you tell me Okay, because of resonance others See you have a partial double one characteristics. Yeah, so basically the electrons are delocalized here in case of carboxylic acid But that kind of resonance is not possible in carbonyl group Yeah, right, right. So correct Next one D What is rosin one reaction? What reagent we use? And what is the product we get here? See what happens in carboxylic acid In carboxylic acid we have this Is the group C double bond o O H So basically the reaction shows by carbonyl compound is what because of this carbonyl group, which is nothing but C double bond o Which can be r r r h l d h ketone anything, right? So here you see in this carbonyl compound This bond is present over here means if I ask you what is the bond order of carbon oxygen bond here the bond ordered will be two But here the bond order is not two because this lone pair is involved in resonance with this spy electron Right. So here what we can say the bond order of carbon oxygen bond here will be more than one But less than two Right. So it has partial double bond characteristics And because of partial double bond characteristics the pi electron density is less over here and here it is more And hence the electron pair shifts over here and then some electrophile comes over here nucleophile comes over here So this kind of reaction shown by Carbonyl group, but since double bond characteristics is not there it has partial double bond characteristics So that's why the carboxylic acid does not give reactions all reactions as to carbonyl group Right. That's the reason Right. So because of this partial double bond characteristics its reactivity decreases In comparison to the molecule which has bond order two or double bond That's the reason So in rosin one reaction what happens we use