 Alright one last video I'm gonna go through the practice test questions that I collected from the test banks that we have in the textbook and same thing I did in class so really nothing new but again something that you can watch as reviewed for the final as you go back through and try to make sure that you're prepped for the whole thing so question number one which of the following is the correct formula for magnesium nitrate magnesium is mg in nitrate from the list of polyatomic ions is NO3 and again you'll know it's on the list of polyatomic ions because of that ATE ending when you see ATE or ITE is a polyatomic ion you go to the table of polyatomic ions you find its formula and its charge there magnesium is in group two of the periodic table there it is group two and group two has a plus two oxidation number nitrate is again on the table of polyatomic ions it's right there it has a negative one charge so the two is going to go to the nitrate the one is going to go to the magnesium we picked the formula that shows that to us one magnesium and two nitrates all right on to question number two what is the correct name for K2 SO4 well K is potassium and SO4 is a polyatomic ion and so again we go to our list of polyatomic ions we find SO4 it tells us that it is sulfate because potassium is a metal we can't use any of those prefixes that we talked about with the covalent substances this is an ionic compound so no monos no dyes no tries etc. and since potassium is in group one there's no roman numeral in the name either so it's just potassium sulfate B is the answer to that so again when you got those polyatomic ions make sure you check the table of polyatomic ions that you'll be given on the reference sheet and check the name whatever that name is the name you use question number three what type of reaction is this well this has no plus sign on the product side and a reaction that has no plus sign on the product side is a synthesis reaction this one's the opposite there's no plus sign on the reactant side no plus sign on the reactant side is decomposition synthesis and decomposition reactions are the two types of reactions that are missing plus signs the synthesis is missing the plus sign on the product side the decomposition is missing the plus sign on the reactant side if it has two plus signs in it it's going to be single replacement those the only three reaction types that you're responsible for knowing on the final exam question number five which of the following combinations would increase the solubility of a gas in a liquid now there's two things that affect a gas they are pressure and they are temperature solids are only affected by temperature and the way it works is that if we're talking about increasing it would be increasing pressure increase the solubility for temperature the way it works you have to decrease the temperature to increase the solubility so we're looking for the one that says something about increasing pressure and decreasing temperature increasing pressure and decreasing temperature see is the answer to that all right on to next which of the following is an Arrhenius acid corner the Arrhenius definition in acid is H and then some negative ion and a base is some positive ion attached to hydroxide those the Arrhenius definitions H something for an acid something hydroxide for a base and again in this question we're asked for the acids we're looking for H and some negative ion that would be a H2S next question again an acid base question this time we're talking about something that is slippery and bitter and Keith being bitter here that's the property that one of the properties anyways that you're expected to know for bases bases are bitter acids are sour you have to know that acids have a pH less than seven bases have a pH greater than seven you have to know what they do to lib this paper so again when you're thinking about acid pH less than seven sour and what this paper ends up red so red stays red blue turns red and for a base a pH greater than seven bitter and blue is the color for lib this paper blue stays blue red turns blue that's what you got to know for your properties of acids and bases here it's all about strong versus weak strong will completely ionize weak partially and this question it says partly ionize so we know it's weak again you have to know this in terms of particle diagrams so if you're looking at a beaker and like our little practice question had the acid is this big open circle with a closed one in the week you're going to have some of that in there some might have broken down but you're still going to have some of that in there and the strong everything will have dissociated everything will have broken apart there'll be no acid or base left number nine the bond between two hydrogen atoms h2 would be what so that's the Lewis structure for h2 it's two hydrogen bond is for the single covalent bond between them both non-metal so we know it's a covalent bond both identical which means the electronegativity difference in this case would be zero each hydrogen has an electro negativity of 2.1 so the difference is zero that makes the bond non-polar covalent if the two atoms are the same the electronegativity difference is zero you'd even have to know what it is and the electronegativity difference is zero they're going to share the electrons equally and that will make a non-polar bond on this one the key is knowing hydrogen has to have two electrons and chlorine needs to have eight in this one chlorine only has two from the double from the single bond here that dash dash represents two electrons so all the chlorine would have around it is two the hydrogen would have four doesn't work for either one of them in this one the hydrogen would have four and the chlorine would have four doesn't work for either one of them in this one the hydrogen would have four and the chlorine would have eight so it works for chlorine doesn't for hydrogen, and in this one the hydrogen has two, chlorine has eight, everything is stable D. Is the correct answer to that one? Again, most elements have to have eight valence electrons to be stable. The exception would be hydrogen here, because it's only got one energy level, and that single energy level can only hold two electrons. Question 11, I'm using Vesper to predict the shape of C, I4. Well C, I4 is five atoms. One carbon, four iodines. And five atom molecules are always tetrahedral. That's about as straightforward as a Vesper question can get. The only one that would be equally easy is the two atom molecule, because two atom molecules are linear. So threes and fours get complicated. All right, number 12. The reason the boiling point of water is higher than the boiling point of hydrogen sulfide is what? Well, one of the things we talked about is intermolecular force. And the stronger the intermolecular force, the higher the boiling point. So if water has a higher boiling point than hydrogen sulfide, then water must have stronger intermolecular forces than hydrogen sulfide. More nomenclature, C, F4. Carbon and fluorine are both non-metals, and because they're both non-metals, that is a covalent substance. And for the covalent substances, we have to use the prefixes, mono, di, tri, tetra, et cetera. We never changed the ending of the first name, so it's just carbon with the appropriate prefix. However, there's only one carbon here, so the prefix would be mono, and we're not allowed to use mono on the first element. So the first word in the name has to be carbon. Automatically eliminates those two. Fluorine becomes fluoride, and the prefix for four is tetra. So carbon, tetra, fluoride is the answer to that question. Percent mass. First thing we got to do is figure out what the mass of sodium chloride is. There's one sodium, each sodium is 23. There's one chlorine, each chlorine is 35. For a total of 58. We're asked for the percent of chlorine in it, so we take chlorine's number, 23, divided by the mass, 58 times 100. Oops, I looked the wrong one, didn't I? Just notice that it's 35, because we're doing chlorine. Yep, chlorine, 35 divided by 58 times 100. So 60.3%. Answer is C. It says 60.7 there, because I just used whole numbers. If I had used some decimal place values in my masses, I would have got the exact same thing. But you can see with our calculation of 60.3, that's the one that's closest, that's the one I pick. All right, moving on. The following molecular formulas for hydrocarbons, which is also an empirical formula. Well, molecular means covalent, and these are all covalent because they're all carbons and hydrogens. Covalent means there's no metals. Empirical means reduced. The one where the subscripts are in their lowest terms and cannot be reduced any further, so the answer is A. We can reduce those by dividing them both by two. We can reduce those by dividing them both by three. We can reduce those by dividing them both by two. Empirical means it is reduced. It's already in its lowest terms. Another reaction type, we got plus signs on both sides. So we know it's not decomposition. Composition, I don't even know what they mean by that. That's probably just a made-up word. And as far as what we have to know, that's a single displacement. And the reason why it's single not doubles, because it's an element in the compound, element in the compound. If you have an element in the compound of both sides, it's single displacement. Again, you're only going to have to know, since this is decomposition and single displacement replacement for the final exam. According to the old study guide. Number 17, the synthesis of ammonia is represented by that equation. We want to completely convert nine moles of hydrogen gas to ammonia, and we want to know how many moles of nitrogen are required. So our two substances are hydrogen and nitrogen. We find hydrogen and nitrogen in our equation up here, and it tells us one mole of N2, one mole because there's nothing in front of the N2, is three moles of hydrogen. This is three in front of hydrogen. So that's our equivalence that we use. This is a mole ratio problem, and your equivalence comes from the balanced equation. Now for the setup, we start with the number that we're given, this nine moles of hydrogen gas. Whatever we're given has to go on the bottom. So the three moles of hydrogen goes in the bottom. The other number, the one mole of nitrogen goes on top. The goal being canceling out that hydrogen nine divided by three is three. So the answer is C. Again, in these mole ratio problems, make sure that you're using the balanced equation to write your equivalence, and your equivalence is just the coefficients from that balanced equation. You've got to find your two substances, and this one's a little tricky because that ammonia gas, we don't need it. In fact, when I was doing this with the eighth period yesterday, I put ammonia in my equivalence before I started, didn't realize until I got here, and started setting up the equation that I didn't need it at all. So again, you got to make sure that you're reading the questions carefully, figuring out what two substances you need, find the two substances in the equation, write the equivalence to your dimensional analysis. Same kind of problem here. That's the equation. We want to know how many moles of oxygen are produced when three moles of potassium chlorate decompose completely. So my two substances are oxygen and potassium chlorate, those two substances. There's a two in front of the potassium chlorate. There's a three in front of the oxygen. So that's my equivalence. Now I do my math, starting with the number from the equation, because I have potassium chlorate as my given. My two moles of potassium chlorate have to go on the bottom so I can cancel that out. My three moles of oxygen go on the top, like so. So you do three times three, that's nine, divided by two is 4.5. So the answer is D. And that's how that's done. Make sure you're good with those, because that's the bulk of what you have to do stoichiometry-wise on the final. Again, I'm not doing any three-step problems because I don't want to confuse anybody with anything else. There's only one of those on the final, so if you miss it, you miss it. There's five throwaways, so I'm not too worried about it. There's more of these though, so I want to make sure you know how to do it. Moving on to the 19, the volume of a gas is .4 liters. The pressure is one atmosphere. At the same temperature, what's the pressure? The volume is 2.0 liters. We got two pressures, we got two volumes. We know this is either Boyle's, Charles, or Gay-Lusak's law, so we go to that part of the reference sheet and we find the equations that has the P's and the V's in it. And it is P1 times V1 equals P2 times V2. Now as far as the ones and twos are concerned, this is where we're starting. We're changing the volume to this. So these are my twos, those are my ones. So it's 1 times .4 equals 2 times P. So it's .4 divided by 2, which is .2. Another gas law problem. The volume of a gas is 5 liters when the temperature is 278 Kelvin. If the temperature is increased to 283 Kelvin, and we're increasing it there so we already know that that's 2 and these are the ones, what will the new volume be? Again, two T's, two V's. We know it's either Boyle's, Charles, or Gay-Lusak's law, so we go to that part of the reference sheet and we find the equation that has the V's and T's in it. And that is V1 over T1 equals V2 over T2. Then we substitute. So it's 5 over 278 equals V2 over 283. So I simplify this side first, divide 5 by 278, and then I'm going to multiply both sides by 283 to move that. So I get 5.08, which rounds to 5.1. And that's how you do that. There'll be some gas laws like that on the final, so make sure you're doing that whole figure out what you got thing so you pick the right equation, substitute, and solve. It's basic algebra. Take your time with it. You've got plenty of time to take the test. Don't mess it up because you're in a hurry. So volume, we're going to calculate the appropriate or approximate volume, that's our variable, of a 0.6 mole sample of a gas, moles of BN at 15 Celsius. Well, we need Kelvin. So we'll add 273 to turn that into Kelvin. That is 288 and 1.1 atmosphere. That's pressure. We have one pressure, one temperature, one amount, and we're looking for volume. There's one of everything that's ideal gas law. PV equals nRT. R is a given, it's on the reference sheet. So we substitute 1.1 times V equals 0.6 times 0.0821. Again, you don't have to memorize that. It's on the reference sheet times 288. Multiply all that together first, 0.6 times 0.0821 times 288, and then divide it by 1.1. Then we have a 12.89, which rounds to 12.9. Again, you'll know it's ideal gas law because there'll only be one pressure, there'll only be one temperature. Nothing will be duplicated, and if nothing is duplicated, it's ideal gas law. If you have duplicates of everything, then it's one of the other gas laws, either Boyles, Charles, or Lusax, and this is the key right here. You have to be going through variables and figuring out what you got, so you can pick the right equation. Don't try to shortcut. Dissociate means ionic. Ionic means it's got a metal in it. The answer is A. 23 as temperature increases solubility of solids. Now, this is the solid thing. The only thing that affects a solid is temperature. Pressure has no effect on it. An increasing temperature would increase the solubility of a solid. Decreasing temperature would decrease the solubility generally. Not always, it's usually, and the reason for that is there are some substances that actually are affected the opposite way, and very few of them. Some that aren't affected at all. Again, very few of them. For almost everything, the solubility goes up. That's why we have this always and usually thing. It almost always does it, but not always. We've got to avoid those terms. Last page of these questions before we get into the ones that I had right, because I couldn't find any good ones in the test banks. 24, I guess those are really long questions. What is the molarity of a solution that contains 125 grams of sodium chloride and 4 liters? The molar mass is 58.44. This is set up exactly the way that you should expect them to be set up on the final. That's what the study guide says. They're going to give you the mass of the solute. They're going to give you the molar mass. They're going to give you the liters. Here's what we do. We'll take the mass we're given, 125, and we'll divide it by the formula mass of 58.44. 125 divided by 58.44 is 2.1-ish. That's the number of moles we have, but that doesn't really matter. You just take the mass of the solute, divide it by the molar mass, you get that number. Then divide that number by the liters of solution. It's about 0.5. That's the answer. Again, this is the way you're going to be given it on the final according to the study guide. They're going to give you the mass of the solute. They're going to give you the molar mass. They're going to give you the liters of solution. Just take the mass that you're given divided by the molar mass, then divide it again by the liters of solution. Acids are sour. One of those properties you have to know about acids. Bases bitter, acids sour. Think lemon juice. Acids react with bases to produce salts and water. It's always H something reacting with something OH. That's acid-base neutralization. The products will always be salt, which is just a general term for anionic compound and water. The H and the OH make the water. We're looking for a conjugate acid-base pair. A conjugate acid-base pair are going to have the same negative ion, and they will only be different by one hydrogen. They will have the same negative ion, and they're only different by one hydrogen. These don't have the same negative ion. Can't be that. These have the same negative ion, so it could be that. These don't have the same negative ion, so it can't be that. These don't have the same negative ion, so it can't be that. We have found our answer. And again, the difference between these two is just that one hydrogen. The acid has the one hydrogen. The base is the one missing it. Now, this one is approached a little differently. The conjugate base of this. So they're telling me this is the acid. We got to find the base, and the way you find the base is by getting rid of a hydrogen. So it's ClO3. Again, a conjugate acid-base pair has the same negative ion. The acid will have one more hydrogen than the base does. That's what you got to remember about it. That's how you spot them. That's how you find them. The greater the average kinetic energy of the particles in a sample of matter. Well, kinetic energy is temperature. Kinetic energy is temperature. If the kinetic energy is going to go up, that means the temperature is going to go up. So the more kinetic energy you have, the higher the temperature. If the kinetic energy is going down, the temperature is going down. If the kinetic energy is staying the same, the temperature is staying the same. So anytime the temperature doesn't change. The kinetic energy doesn't change either. Temperature is kinetic energy. That's what they want you to know. A catalyst lowers activation energy. That's what they do. Remember those humps in the potential energy diagrams? Have to get over the hump for the reaction to happen. Catalysts lower the hump. That's what they do. They lower the activation energy. Mole particle conversion. You've got to know one mole equals 6.02 times 10 to the 23rd of anything. That's Avogadro's number. You have to know Avogadro's number. It's not on the reference sheet. Whenever you're given atoms you will divide by Avogadro's number. So it's important we put this in the calculator right. Just move this up. Now my calculator, it's this times 10 to the X button. On the calculators that are over there on the wall, it's the EE button that you would be pushing. So what you do is you put this number in first and we do 4.8. Then we hit the exponential notation key EE or exp and then 25. Then we hit divided by Avogadro's number. 6.02 EE 23 equals. At no point do I ever actually type in times 10. That's what the EE button is all about. I didn't type in times 10 to get that to show up. I just pushed the exponential notation key and it showed up. 79 is 80. Rounded and that is 80 in scientific notation. They just put this in there for significant figures. That scientific notation thing. Now if we're given moles we're going to divide by or not divide by multiply by Avogadro's number to find the atoms. We'll do the opposite math process. If we're given atoms we divide by Avogadro's number. If we're given moles we're going to multiply by Avogadro's number. So 0.075 times 6.02 EE 23 is 4.5 times 10 to the 20 seconds. And again my calculator actually says times 10 to the 22nd. The ones on the wall don't put the times 10 there. So it's 4.515 and then there's an exponent 22 in it. That little exponent 22 is that. And in the last one molar mass of AUCL3 there's only one AU. The mass of AU from the periodic table is 197. And then we go find the mass for chlorine 35. But there's three of them. So I do 35 times 3. That's 105. Then I add them up. And I get 302. Again they have 303.6 because they're using those decimal place values. Again if you use the whole numbers you're fine because there's only one thing that's even close to 302 there. It's kind of easy to pick out which is which. Now I'm going to pause this video for a second so I can print out the other I can find a copy of the other ones actually. I think they're right here. Here we go. Here they are. Now 8th period I didn't get to go through these on the board with you because I didn't have them in my little smart notebook thing whatever they call it. But I do have it here so we can actually look at it on the video so you can see what you missed out on yesterday. Everybody else will see it because I'll take pictures of it today. Which of the following correctly represents the effect of a catalyst? Again catalyst lower activation energy. Activation energy is the height of the hump. It lowers that so D is the answer. What element does that represent? What it's asking you what element does it represent? You're just counting the number of arrows. The arrows will tell you the atomic number. So 2, 4, 6, 7, 8 arrows means it's atomic number 8 and atomic number 8 is oxygen. When calcium ionizes what noble gas will it resemble? Well it's a metal. Calcium is a metal because it's over on the left side of the periodic table. There it is. It's going to lose electrons to become stable specifically because it's in group 2. It's got two valence electrons. It'll lose two electrons to become stable. So it'll change from having 20 electrons to having 18. So it will look like argon, the noble gas that comes before it on the periodic table. Metals look like the noble gas that come before them. Non-metals look like the noble gas that come after them. And finally last but not least which of these represents the law of conservation of mass that means they have to have the same things on both sides. Don't have to go far. It's the first one. One black circle, one black circle, two white circles, two white circles. This one doesn't have enough black circles so it doesn't work. This one doesn't have enough white circles and it's got one extra black one so it doesn't work. And this one has lost a black one so it doesn't work. You've got to have the same thing on both sides for law of conservation of mass. That's it. That's all the videos I'm posting. We're not doing any more review sheets or anything like that. We've reviewed everything multiple times so watch the videos, go back over the review sheets, and do your best to make sure you pass the final.