I don’t understand last years Free response question about equilibrium (number 4) the question states that Caco3 decomposes into CaO and CO2. The equilbrium pressure of the system is 1.04 and part of the question states that if more CO2 was injected into the container would the pressure go up down or stay the same. College board said it would stay the same but I don’t understand. Kp value is the ratio of products to reactants and usually it would stay the same cause even though there is more moles of each the ratio stays the same. However, CaO and CaCO3 are emitted from the expression because they are solids so wouldn’t the Kp go up because there is slightly more moles of CO2 even after it reestablishes equilbrium. The molarity would be higher and that molarity would be the same value as the Kp value. Can someone please explain why the answer is that it stays the same and does not go up? Thank you.
LeChatelier’s Principle can be used to evaluate the possibilities. The pressure would return to equilibrium, even if it briefly changes, because the products would convert to reactants or vice versa (sorry, I’m not looking at the question right now) to reduce/increase the pressure until it once again reaches the equilibrium pressure.
So I just took the Crash Course Test and got a 4. It was pretty accurate in comparison with the 2014 exam. What else should I do to review? I have Princeton, 5 steps to a 5, and Crash Course for Chem. Basically I have more books than days at this point.
What can I do for review at this point? More practice tests or just study? And should I go over the 2014 FRQ in detail?
A good video for titrations: https://www.youtube.com/watch?v=kOOOuny8G-o
Are the nmsci notes good enough? (For a last minute review)
I got the cracking the ap chemistry 2015 version i did all the review questions and there was not one question about any of those ( the changing of the bp,vp,fp)
Yes smargent is correct, they say 1.04 is the pressure at equilibrium so anything that disturbs equilibrium will be reversed so that it gets back.
Princeton Review 2015’s book has 60 questions at practice exams. is it true? 75 or 60?
@spincrus 60
And it’s now 4 choices, not 5 on the mc
I scored 40/60 in MC. So, what percantege should I score in FRQ to score 5 in general
Also, will there be nuclear chem?
Spincrus you would need at least 66%
theres no nuclear chem, molality, freezing and boiling point depression in ap
~66%
No.
^I heard that the new curve requires you to score 70%+ to get a 5? Are you sure that 40/60 and around 2/3 of the frq points will be enough? That would be awesome if it really is. It would be greatly appreciated! And do you guys think it would be a good use of my time to practice frq’s from past years? How much did the 2014 frq change? Is there still going to be equation writing? Lol sorry for all the questions, I’m just freaking out like everybody else :/. 2 days left…
Well, nobody know’s what this year’s curve will be because it is in the future. But based on LY’s, 65-67% should be in the ballpark.
Just for some perspective, I think it’s pretty comical/interesting that if you get 60% on mc, you’d need only 20% on free response to get a 3!
@skieeurope: Oh ok, thanks. I thought the curve changed in 2014 or something.
Also, I have the 2002, 2008, and audit AP chem exams if anyone wants to trade with me…
Considering you needed a 72% last year why would they drop it to a 66-67 @skieurope?