For more information, please see full course syllabus of AP Chemistry

For more information, please see full course syllabus of AP Chemistry

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### AP Practice Exam: Multiple Choice, Part II

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

- Intro
- Multiple Choice
- Multiple Choice 42
- Multiple Choice 43
- Multiple Choice 44
- Multiple Choice 45
- Multiple Choice 46
- Multiple Choice 47
- Multiple Choice 48
- Multiple Choice 49
- Multiple Choice 50
- Multiple Choice 51
- Multiple Choice 52
- Multiple Choice 53
- Multiple Choice 54
- Multiple Choice 55
- Multiple Choice 56
- Multiple Choice 57
- Multiple Choice 58
- Multiple Choice 59
- Multiple Choice 60
- Multiple Choice 61

- Intro 0:00
- Multiple Choice 0:12
- Multiple Choice 42
- Multiple Choice 43
- Multiple Choice 44
- Multiple Choice 45
- Multiple Choice 46
- Multiple Choice 47
- Multiple Choice 48
- Multiple Choice 49
- Multiple Choice 50
- Multiple Choice 51
- Multiple Choice 52
- Multiple Choice 53
- Multiple Choice 54
- Multiple Choice 55
- Multiple Choice 56
- Multiple Choice 57
- Multiple Choice 58
- Multiple Choice 59
- Multiple Choice 60
- Multiple Choice 61

### AP Chemistry Online Prep Course

### Transcription: AP Practice Exam: Multiple Choice, Part II

*Hello, and welcome back to Educator.com, and welcome back to AP Chemistry.*0000

*We are going to continue our multiple-choice practice, and we left off at problem #41, so we are going to start with problem #42: let's just jump right on in.*0004

*OK, when the equation above is balanced and all coefficients reduced to lowest whole-number terms, the coefficient of OH ^{-} is going to be...*0013

*All right, so 42: this is just a simple balancing issue, so when you balance this out, the coefficient of the OH ^{-} is going to be 3, so 42 is C.*0021

*OK, #43: A sample of 61.8 grams of H _{3}BO_{3} (a weak acid) is dissolved in 1,000 grams of water to make a 1 molal solution.*0034

*Which of the following would be the best procedure to determine the molarity of the solution? Assume no additional information is available.*0046

*OK, of these choices, the best way to check the molarity of the situation...because molarity is moles per liter, you need the total volume, which is in the denominator of molarity; it actually is going to be D.*0055

*You need to take a measurement of the total volume of the solution.*0068

*That is it--nice and straightforward.*0072

*OK, #44: A rigid metal tank contains oxygen gas (rigid, so there is no volume change).*0076

*Which of the following applies to the gas in the tank when additional oxygen is added at a constant temperature?*0084

*That is the important part: additional oxygen is added at a constant temperature.*0091

*"The volume of the gas increases"--no, it's rigid.*0097

*"The pressure of the gas decreases"--no, you are actually injecting gas into the system, so the pressure actually increases.*0100

*"The average speed of the gas molecules remains the same"--this is where it is a little bit tricky.*0107

*Now, a constant temperature: that is the secret here--a temperature constant implies that the average kinetic energy is unchanged.*0114

*Remember, temperature is a measure of the energy of the actual molecules: if the temperature doesn't change, the average energy of the molecules doesn't change.*0125

*So, that is unchanged.*0134

*Well, that means one-half the mass times the average velocity squared is unchanged; this means that the velocity, the average velocity, is unchanged.*0140

*So, yes, C is the answer for #44.*0151

*OK, #27 What is the hydrogen ion concentration in a .05 Molar HCn?--the K _{a} for HCn is 5.0x10^{-10}.*0156

*OK, so again, this is a weak acid problem; we do have to use an ICE chart, but again, the numbers are going to be really, really simple, so there doesn't have to be any complicated calculations.*0168

*Let's go ahead and run through what we normally run through.*0181

*The number of species in solution: well, we have HCn in solution, and we have H _{2}O in solution.*0186

*Of those two things that can dissociate, the 5.0x10 ^{-10} K_{a} for HCn...this is the dominant equilibrium, so what we are going to have is the following.*0192

*We are going to have: HCn is in equilibrium with H ^{+} + Cn^{-}.*0203

*Well, they tell us that the...so we are going to have an Initial; we are going to have a Change; and we are going to have an Equilibrium.*0210

*They tell us we have a .05 Molar, so before anything happens, there is none of this, and there is none of that.*0215

*I'm sorry, I shouldn't say they don't matter; I'll use 0; we use straight lines for things that actually are irrelevant.*0221

*A certain amount is going to dissociate; a certain amount is going to show up; and a certain amount is going to show up.*0228

*We are looking for x, because that is going to be the hydrogen ion concentration.*0232

*0.05-x, x, and x; so they tell us that the K _{a}, which is 5.0x10^{-10}, equals this times that, divided by that.*0236

*We get x ^{2} over 0.05-x, which is just about equal to x^{2} over 0.05.*0253

*OK, and when I do that calculation, I end up with (so now we go over here; we end up with) x ^{2}=0.25x10^{-10}; that means x is equal to the hydrogen ion concentration (right?--x is hydrogen ion concentration); it is equal to 0.5x10^{-5}.*0264

*Square root: just basically take the square root of .25 and the square root of 10 ^{-10}, and then, when you convert this to scientific notation, you end up with (oh, these stray lines are crazy! OK) 5.0x10^{-6}.*0292

*That is D, so our answer for 45 is D.*0311

*Again, set up your ICE chart; the numbers are really easy to work with--nice and straightforward.*0316

*OK, so #46 says: Which of the following occurs when excess concentrated NH _{3} is mixed thoroughly with .1 Molar copper nitrate, aqueous?*0322

*OK, so we have a copper nitrate solution; a copper nitrate solution is going to be a colored solution.*0336

*It is a transition metal: most transition metals are colored--they absorb visible light.*0343

*And again, like I mentioned earlier, the copper nitrate dissolves; the water molecules surround the copper (2 of them, 4 of them, 6 of them...however many); there is a certain color that that complex ion absorbs.*0349

*When you put NH _{3} into this solution, well, the NH_{3}...a couple of molecules of ammonia may actually replace a couple of molecules of water surrounding the copper ion.*0363

*What happens is: the color actually gets darker or changes or gets lighter; so, in this case, the best choice would be: The color of the solution turns from a light blue to a dark blue; so the answer would be C.*0374

*OK, #47: When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2% hafnium by mass and 37.4% chlorine by mass; what is the empirical formula of the compound?*0390

*OK, so this is a straight empirical formula problem where you convert percentages to grams; you can go to moles and divide by the least number, and you should be able to get some whole numbers.*0410

*Let's go ahead and do this really quickly: Hafnium--we have 62.2%, is 62.2 grams, times 1 mole of hafnium is roughly 179 grams; so I end up with about...one-third; so let's go ahead and put .34 (I'll round it slightly up, because this is a little bit more than that).*0419

*When I do chlorine, that is going to be...they say 37.4%, which is 37.4 grams times 1 mole/35.45 grams, so you are looking at about 1.*0448

*So now, we go ahead and divide by that to get 1; 0.34...you get 3; there is your answer, HFCl _{3}; it looks like C is your final answer for #47.*0464

*OK, #48 says: if 87.5% of a sample of pure iodine-131 decays in 24 days, what is the half-life of iodine-131?*0482

*Well, we know what the half-life of something is: that is the amount of time it takes for half of a sample to vanish.*0498

*OK, this 87.5%...again, on these AP exams, you are going to be given very easy numbers to work with.*0505

*Here is what happens: I start with a sample; OK, half of it decays; now I am left with 50%.*0512

*Well, now half of that sample decays; well, half of 50% is 25%, so now, I am at 75% of the original sample (is gone).*0522

*Now, half of...so now I have 25% of the sample left; well, half of that 25% is 12 and a half percent; so after three cycles of half-life, half-life, half-life, 75 plus another 12.5 puts me at 87.5.*0533

*So, after 3 cycles...the original sample--half goes away; what is left over--another half goes away; what is left over--another half goes away; at that point, I have 87.5% that has decayed.*0552

*Well, I have three cycles; 24 days to go through three cycles; that means each cycle is 8 days long, so the half-life of iodine-131 decay is 8 days.*0568

*Take a look at the percentage, and chances are it is either going to be 1, 2, 3, or 4; and then, just take the number of days or hours or minutes or seconds and divide by the number of cycles.*0582

*We went through one cycle, two cycles, three cycles; 24 days; 3 into 24 is 8 days; so 48 is B.*0592

*I hope that makes sense.*0604

*OK, #49: Which of the following techniques is most appropriate for the recovery of solid potassium nitrate from an aqueous solution of potassium nitrate?*0606

*If you have an aqueous solution, and you need to recover the solid, it's very simple: just boil off the water--so "evaporation to dryness"--49 is E.*0615

*OK, #50--let's see: #50 says: In the periodic table, as the atomic number increases from 11 to 17, what happens to the atomic radius?*0628

*As you move from left to right on the periodic table, atomic radius (not ionic radius, atomic radius) decreases.*0641

*As the positive charge gets bigger, even though you are adding one electron, you are actually going to be sucking in the electrons a little bit more.*0649

*So, as you move from left to right (from your perspective, left to right on the periodic table), the atomic radius gets smaller.*0656

*The answer is D: it decreases only.*0662

*OK, #51--let's see what we have: Which of the following is a correct interpretation of the results of Rutherford's experiment, in which gold atoms were bombarded with alpha particles?*0667

*Well, you remember the Rutherford scattering experiment: he shot alpha particles (which are helium nuclei) at a thin piece of gold--through a thin piece of gold--and very few of the alpha particles actually ended up bouncing backward.*0680

*Most of the alpha particles just passed right on through.*0697

*What that means is that the positive charge of the atom is concentrated in a very small region.*0701

*An atom like this--a positive charge is actually concentrated in a very tiny part of it; most of the alpha particles just pass through the atom.*0706

*So, 51 is E.*0715

*OK, #52: Under which of the following sets of conditions could most O _{2} be dissolved in H_{2}O?*0722

*OK, if you are trying to dissolve a gas in a liquid, what you need is high pressure, low temperature.*0730

*So, here: high pressure--let me see: we look at 5 and 5 atmospheres (that is A and B); low temperature--between 80 and 20, we are going to take the 20 degrees, so we will take B.*0737

*52 is B; so, again, when you need to dissolve a gas in a liquid, you need conditions of high pressure, but you need conditions of low temperature.*0751

*If the liquid actually is a high temperature, it is going to be bubbling, bubbling, bubbling; it is going to be all excited; high temperature is actually going to force the gas out.*0761

*Low temperature means the gas can actually occupy a space in that liquid.*0769

*All right, let's see--#53: OK, gases W and X react in a closed, rigid vessel to form gases Y and Z according to the equation above; the initial pressure of W is 1.2 atm, and that of X is 1.6 atm.*0775

*No Y or Z is initially present; the experiment is carried out at constant temperature; what is the partial pressure of Z when the partial pressure of W has decreased to 1 atmosphere?*0796

*OK, so let's work this one out; it is actually very, very simple.*0809

*W gas, plus X gas, goes to Y gas plus Z gas.*0814

*They tell me this is initially at 1.2 atm, and this is at 1.6 atm.*0825

*It is 0 and 0 here; so at the end, when this is dropped down to 1 atmosphere, they want to know what is the concentration of...yes, what is the partial pressure of Z.*0832

*OK, now, notice what they said...equation...container...carried out...OK, here is what is important: the experiment is carried out at constant temperature.*0851

*Because it is carried out at constant temperature, that means nothing actually changes in terms of pressure.*0860

*So, the beginning total pressure, which is 1.2 plus 1.6 (which is a total of 2.8)--that is going to actually end up being the final pressure: 2.8.*0865

*Now, the final pressure consists of the pressure of the W, the X, the Y, and the Z.*0877

*Now, pressure is the same as concentration (right?--pressure and concentration are just different sides of the same coin): now, this pressure went from 1.2 to 1.0.*0884

*Well, this is a 1:1 mole ratio; so, if .2 moles of this was used up, I can think of pressure as just moles.*0895

*.2 moles of this was used up: that means this pressure dropped down to 1.4.*0903

*Well, this is 1:1; if .2 moles was used up, that means .2 moles of this was formed, and .2 moles of this was formed.*0908

*So now, we want the total pressure to be 2.8.*0919

*Well, 1, 2.4, 2.6, 2.8; that is how you work out this problem; the idea is constant temperature--that means pressure doesn't change: the initial pressure equals the final pressure.*0924

*You use the mole ratios, and you use the fact that pressure is like concentration: if this pressure drops from 1.2 to 1.0, since this is 1:1, this one drops, also, from 1.6 to 1.40.*0937

*Well, if this loses .2 atmospheres, there is gain of .2 atmospheres here, gain here; as long as the sum of those equals the sum of this, everything is fine.*0951

*So, 1.2 is the answer: so we get: 53 is equal to A.*0963

*OK, #54: Let's see, which of the following changes alone would cause a decrease in the value of K _{eq} for the reaction represented above?*0972

*OK, so they say that we have: 2 NO gas, plus O _{2} gas, is in equilibrium with 2 NO_{2}; and they tell me that this ΔH is less than 0, which means that it is exothermic.*0989

*Exothermic means that it releases heat, so I'm going to write +heat; heat is one of the products.*1006

*Now, which of the following changes alone would cause a decrease in the value of K _{eq} for the reaction represented above?*1012

*Let's see: if you decrease the temperature...no, if you decrease the temperature, it is going to want to increase the temperature, so the reaction is going to go to the right.*1021

*Decreasing the value of K _{eq} means pushing the equilibrium to the left, backward towards the reactants: the only thing here that does that--if you increase the temperature, which means increasing the heat, that means you are going to increase one of the products, which is heat.*1031

*Well, the system is going to offset; it is going to offset by wanting to move to the left.*1049

*A reaction that moves to the left: that means the equilibrium constant is actually--all things being equal, the equilibrium constant will decrease.*1055

*That is what you have recognize: a decrease in the value of K _{eq} means that more of the reactant is going to be favored.*1067

*In this particular case, because it's exothermic, by increasing the heat--increasing the temperature--you are forcing the reaction to move to the left.*1074

*I hope that makes sense; so here, 54--the best answer is B.*1086

*OK, #55: According to the balanced equation above, how many moles of HI would be necessary to produce 2.5 moles of I _{2}, starting with 4 moles of KMnO_{4} and 3 moles of H_{2}SO_{4}?*1092

*OK, this is basically just a limiting reactant problem; so we need to find out...we need to just look at the equation to see...which is which.*1110

*Let me actually write this equation out...you know what, that is fine; we can just work right from the page; we don't really need to write anything out--there is nothing too complicated going on here.*1119

*We want to produce 2.5 moles of I _{2}, starting with 4 moles of KMnO_{4}.*1130

*OK, so we have 4 moles of KMnO _{4}; how many moles of HI?...and 3 moles of H_{2}SO_{4}.*1136

*OK, so we have 3 moles of H _{2}SO_{4}; for that, 2 moles of KMnO_{4} are necessary; well, we have 4 moles of KMnO_{4}, so that is not a problem.*1145

*3 moles of H _{2}SO_{4} requires 10 moles of HI (right?--because there is a 10 in front of the HI).*1155

*10 moles of HI gives 5 moles of I _{2}; in order to produce 2.5 moles of I_{2}, which is half of 5, I need half of 10.*1162

*Therefore, I need 5 moles of HI; so the answer is D.*1171

*That is it: just look at the mole ratio; see which one is the limiting reactant (in this case, the H _{2}SO_{4}); the rest is just mole ratios.*1175

*And again, the numbers are very, very simple.*1183

*OK, #56: A yellow precipitate forms when .5 Molar NaI is added to a .5 Molar solution of which of the following ions?*1186

*OK, so you have sodium iodide: sodium is not going to do anything--it is going to be soluble with anything; iodide ion is not going to mix with chromate, sulfate, or hydroxide, and it is going to be soluble with zinc; so A is your final answer.*1196

*Lead iodide: that is the one that is the yellow precipitate.*1210

*OK, #57: Let's see, according to the information above, what is the standard reduction potential for the half-reaction M ^{3+} + 3 electrons goes to M, solid?*1215

*OK, we need to look at what they gave us; we need to rearrange it in such a way that, when we add it, we get what we want, which is: M ^{3+} + 3 electrons goes to M(s).*1229

*All right, now notice what they want: the M ^{3+} is on the left; what they give us--the M^{3+} is on the right; so I'm going to flip that first equation.*1240

*I'm going to write that first equation as (oops, let me write--this is #57)...I'm going to write: 3 Ag, solid, plus M ^{3+}, goes to M, solid, plus 3 Ag^{+}.*1249

*Now, the potential for that is +2.46, but since I flipped the equation, now the electric potential is going to be -2.46 volts.*1273

*Now, I have an Ag ^{+} on the right, and the other equation they give me has an Ag^{+} on the left; so I'm going to leave that as written.*1283

*Ag ^{+} + an electron goes to Ag, solid.*1291

*Let's see: the electrostatic potential for that is positive 0.80, because I haven't done anything to it.*1308

*However, I am going to go ahead and put a 3 in front of the Ag, 3 in front of the electron, and 3 in front of this Ag, because the final equation that I am looking for--I need the Ag's to cancel.*1317

*This cancels with that; that cancels with that; and I am left with: M ^{3+} + 3 electrons goes to M, solid--which is exactly what I wanted.*1327

*Now, I just add these two, and I end up with -1.66 volts, which is A.*1339

*That is it; I just need to arrange this in such a way...now, the only thing you have to remember here is: notice, I change this second equation by actually multiplying everything by a 3.*1350

*However, this is not like enthalpy: reduction potential is an intrinsic property--it doesn't depend on how much of something you have; it is just a property.*1361

*So, even though I put 3 here, I didn't multiply the electrostatic potential by 3; the only thing that I change when I change electrostatic potentials is the sign, if I flip the equation.*1373

*Flip the equation--just go positive/negative, negative/positive; but by adding coefficients in order to make things cancel, I do not change the electrostatic potential.*1385

*It is not like enthalpy or entropy or free energy; OK, so very, very important: electrostatic potential is an intrinsic property--does not depend on the amount that you have.*1394

*If this were enthalpy and we were doing Hess's Law, yes, you would have to multiply this by 3; OK.*1403

*Let's see, where are we?--we are at #58.*1411

*OK, #58: On a mountaintop, it is observed that water boils at 90 degrees Celsius, not at 100 degrees Celsius, as at sea level.*1415

*This phenomenon occurs, because on the mountaintop...of our choices, C is the best choice.*1425

*Equilibrium water vapor pressure equals the atmospheric pressure at a lower temperature.*1433

*Remember what boiling point is: the boiling point is the temperature at which the vapor pressure is equal to the atmospheric pressure.*1439

*As you go higher in elevation, the atmospheric pressure drops; there is less atmosphere, so there is less pressure.*1448

*Well, because there is less pressure, you reach vapor pressure at a lower temperature.*1454

*That is why boiling point decreases as you go higher in elevation; so C is the best answer here.*1460

*OK, #59: Let's see, a 40-milliliter sample of a .25 Molar KOH is added to 60 milliliters of a .15 Molar BaOH _{2}.*1468

*What is the molar concentration of OH ^{-} in the resulting solution?--assume that the volumes are additive.*1479

*OK, so we need to calculate the total moles of OH ^{-} and divide by the total volume.*1485

*All right, so we know that potassium hydroxide dissociates as 1:1: one mole of potassium hydroxide produces one mole of hydroxide ion.*1491

*Let's go ahead and do that one: that is going to be 40 milliliters, times 0.25 millimoles per milliliter (moles per liter--I can do millimoles per milliliter, or centimoles per centiliter, as long as I do it consistently); so I end up with 10 millimoles of OH ^{-}.*1501

*Now, barium hydroxide (BaOH _{2}): when it dissociates, it produces 1 mole of barium 2+, but it produces 2 mol of hydroxide.*1524

*Here, I have 60 milliliters times 0.15 millimole per milliliter, and then I multiply that by 2 moles of OH ^{-} per one mole of barium hydroxide; I end up with 18 millimoles.*1534

*Or, I could have just done this first calculation and gotten 9 and just multiplied by 2, because 1 mole of this produces 2 moles.*1556

*So now, I have a total of 28 millimoles of OH ^{-}, and I divide by my total volume, which is 40 milliliters plus 60 milliliters, which is 100 milliliters; so I get a molarity of 0.28 M.*1563

*Now, you notice: if you remember, my m has a line on top of it; the molarity symbol that is used nowadays is a capital M; so you will see it as .28 M.*1583

*There you go; that is your answer, and .28 is C.*1594

*#59 is C; all right.*1599

*Just a couple more to go here for this lesson: let's see, #60 says: A .03 mole sample of NH _{4}NO_{3} is placed in a 1-liter evacuated flask, which is then sealed and heated.*1603

*The NH _{4}NO_{3} decomposes completely according to the balanced equation above.*1621

*The total pressure in the flask is measured at 400...I'm sorry, the total pressure of the flask is measured at 400 Kelvin; it is closest to which of the following?--and they give you the value of R; OK.*1627

*Here, we need to find the total number of moles of gas that is produced; we have a solid, and it is evacuated, so the pressure is 0 to begin with, but you are producing N _{2} gas and H_{2}O gas.*1644

*OK, well, let's see: we have .03 moles...so let's go ahead and write our equation here.*1657

*We have: NH _{4}NO_{3}--that is a solid--and it is going to form 1 mole of N_{2} gas and 2 moles of H_{2}O gas--2 moles of that.*1665

*Well, if I have 0.03 moles of this to start off with, 1:1 ratio, it is going to end up forming .03 moles of this; 1:2--it is going to end up forming .06 moles of that; the total number of gas that is going to be floating around in that container is going to be 0.09.*1683

*So now, we use our PV=nRT; the total pressure is equal to nRT over V; number of moles is 0.09; 0.082 is what they give us for R; the temperature is going to be 400; and then, it is in a one-liter flask.*1705

*When you multiply all of this out (which you should be able to do just on sight): .09, .08, times 400...you are looking at about 2.95; the answer is going to be 3 atmospheres.*1730

*So the answer is A; so 60 is A--that is it.*1745

*You want to find the total moles of gas, and then just use the ideal gas law to find the pressure.*1750

*OK, #61: For the reaction of ethylene represented above, ΔH is -1323 kilojoules.*1756

*What is the value of ΔH if the combustion produced liquid water, rather than water vapor?*1766

*ΔH for the phase change of H _{2}O gas to H_{2}O liquid is -44 kilojoules per mole.*1773

*OK, so we have this reaction: C _{2}H_{4} + 3 O_{2} gas forms 2 moles of CO_{2} and 2 moles of H_{2}O.*1781

*They tell me that the ΔH for this is equal to -1323 kilojoules.*1794

*Notice, it is not kilojoules per mole; it is kilojoules.*1800

*OK, now, this H _{2}O is as a gas; well, they are saying, "What would happen to the ΔH if, instead of forming water vapor, it actually formed liquid water?"*1803

*Well, they are telling me that the ΔH for the phase change of H _{2}O gas to H_{2}O liquid...they are telling me that the ΔH for this process is equal to -44 kilojoules per mole.*1815

*Here we have to watch a couple of things: we have to watch the direction, and we have to watch the units.*1838

*This one is in kilojoules; this is in kilojoules per mole.*1843

*Well, we have 2 moles of water that are going to go from gas to liquid; OK.*1846

*Here is what this looks like: the final ΔH is going to be the sum of the ΔH's, so we are going to start with -1323 kilojoules, and we are going to add...*1852

*Now, in going from a gas to a liquid, you are actually giving off heat, which is what this negative 44 says; so, we are going to add the heat given off in going from gas to liquid.*1865

*But notice: we have 2 moles of water (let's get rid of these crazy lines that are showing up all over again), so we have -44 kilojoules per mole, times 2 moles, because we have 2 moles of water that is going from gas to liquid.*1879

*That does that; when we actually do this, 2 times -44 is -88; -1323 plus a -88...our final answer is -1411 kilojoules, and that is E; so 61 is E.*1904

*OK, thank you for joining us for the second part of the multiple choice; we have one more section to go.*1926

*So, thank you for joining us here at Educator.com.*1931

*We'll see you for the next lesson; goodbye.*1933

1 answer

Last reply by: Professor Hovasapian

Sun Feb 22, 2015 7:37 PM

Post by Shih-Kuan Chen on February 21, 2015

Professor, where can I learn more about flame color and colors of ions and compounds?

0 answers

Post by Mwongera Mwarania on October 27, 2013

Sorry, on re-listening the recording, you have explained that e0 is not like Enthalpy: you don't multiply with. You only reverse the sign if you reverse the reaction. Please ignore my earlier question.

0 answers

Post by Mwongera Mwarania on October 27, 2013

Q.57: Why did you not multiply the e0 by 3 for the second step in accordance with the Hess' law?

0 answers

Post by Professor Hovasapian on July 18, 2012

Link to the AP Practice Exam:

http://apcentral.collegeboard.com/apc/public/repository/chemistry-released-exam-1999.pdf

Take good Care

Raffi