@rhubarbb Let’s start with what you do understand. In Cu(s) + 2Ag^+1(aq) → Cu^+2(aq) + 2Ag(s) galvanic cell, where Ag+ is removed, you are correct in saying that the reaction quotient would increase because you’re dividing by a smaller number. It might be a mistake on Barron’s part. The general formula is Q = [products]/[reactants] at any other concentration besides when the system is at equilibrium. The initial state is probably assumed to be at equilibrium before they take away the Ag+. Therefore, the system shifts to the left to compensate for the lost Ag+, because Q > K, with K being before Ag+ removal, and Q after.
As for voltage, the equation used you might have to memorize. It’s not one of the equations provided on the AP Chemistry Exam equation sheet. The equation is known as the Nernst equation, for Walter Nernst’s namesake. A commonly manipulated form of the equation is : E = E° - [ 0.0592/ n] log(Q) where E is your answer for the new voltage, E° is the standard cell potential, n the number of moles of electrons used in the balanced half reaction equation. As the concentrations change in the cell, Q changes, followed by E.
**To calculate at a different temperature other than standard, you would use E = E° - [RT / nF]ln(Q).
Actually our teacher gave us the same test and said, historically, it should be 65% based off of the old test. He’s been at this game for a LONG time. He also went on to note that there is NO conversion score factor provided by college board and any “conversions” are based off of pure conjecture, off of a single test that no body knows anything about. Basically, no one knows because CB is trying to keep hush hush. So we don’t know! The only things we can do is try our best! Good luck!
Yea, @alecdtatum is right, my teacher showed us the conversion table. However, the 2014 exam that teachers have has 10 less questions for mc, (50 not 60) so the actual conversion table could have been a bit higher or lower for a 5.
Thanks for the link btw @alecdtatum
@rhubarbb I don’t think I’ve seen a single reference to plasma in this class this whole year, through the curriculum, old format tests and new format tests. So I think it’s safe to assume it’s not on the exam
There were some issues with the FR length on the 2014 exam. Search the following page for Chemistry. It lists the Trevor Packer tweets when scores for 2014 were released:
Hey guys, how are you going to prepare for the exam? I already took a chemistry AP course in school and now i need to prepare myself for the exam so where can i get sample questions and explanations since there is only 1 past paper that i solved
Hey guys! I know that you do not have to know about colligative properties or molality for the new test, but does that also mean that we do not have to know about freezing point depression, vapor pressure lowering, and boiling point elevation?
@nparker@alldaboston all the concepts you just listed will NOT be on the new exam. There was a heating curve on last year’s exam, but even if you didn’t know anything about a heating curve, you could have gotten the 3 questions associated with it correct. The test writers, as expected, incorporated other concepts into the heating curve questions (IMF, enthalpy of rxn, etc.)