Kaplan Practice problem

[DAT24]

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I did not get the right answer for this but feel the solution is wrong:

An ideal gas is placed in a 10 liter container that is free to expand. If the temperature (K) is doubled and the pressure is changed from 60 mmHg to 20 mmHg, what is the new volume in liters?

A. 20/60 x 1/2 x 10

B. 20/60 x 2 x10

C.60/20 x 1/2

D. 60/20 x 1/(2 x10)

E. 60/20 x 2 x 10 (correct answer)

Thanks in advance!

 

[DAT24]

Here is another:

Trial [A]o (M) o (M) rate (M/min)
1
1 x 10–2 3 x 10–3 2 x 10–3
2 1 x 10–2 6 x 10–3 8 x 10–3
3 2 x 10–2 1.2 x 10–2 3.2 x 10–2


17. What is the reaction order with respect to A?
A. 1
B. 1.5
C. 2
D. 3
E. 0

I thought the answer was c but the solution gives E as the correct answer.

I think I discovered my error, there is no trail B that has the same concentration to determine the order for A, correct?

 

[JamesBourne]

I did not get the right answer for this but feel the solution is wrong:

An ideal gas is placed in a 10 liter container that is free to expand. If the temperature (K) is doubled and the pressure is changed from 60 mmHg to 20 mmHg, what is the new volume in liters?

A. 20/60 x 1/2 x 10

B. 20/60 x 2 x10

C.60/20 x 1/2

D. 60/20 x 1/(2 x10)

E. 60/20 x 2 x 10 (correct answer)

Thanks in advance!

Deriving from PV=nRT equation, PV/T(1)=PV/T(2), initial conditions: volume-10L, pressure-60 mmHg temp.- lets make it T, final conditions:volume- x(one we are looking for), pressure-20 mmHg, temp- 2T, now lets plug and chug
(60mmHg*10L)/T = (20mmHg*X)/2T, cross multiply to solve for x, and we get 60 for the final volume which is E

 

[aecap0990]

they're both right.
for the first one, (P1*V1)/T1 = (P2*V2)/T2
so you end up with 60*10/1 = (20*V2)/2
rearrange and you get E (they don't give you an actual temperature, but since T2 is double T1, you can just use 1 and 2 since you don't need to calculate an actual number

for the second one, determine the rate with respect to B first. you'll see that from trial 1 to 2, A stays the same and B is doubled, which makes the rate X4, so rate is 2nd with respect to B. now when you look at trial 2 to 3, you see that B has doubled so you automatically know rate will be X4 which is confirmed when you look over at the rate from 2 to 3. however, you had also doubled A from 2 to 3. since rate only increased X4, you know A had no affect so the order must be 0 for A

 

[DAT24]

Thanks I appreciate it, I caught my mistakes when I looked over them the second time.🙂

 

[demolitionlvr]

they're both right.
for the first one, (P1*V1)/T1 = (P2*V2)/T2
so you end up with 60*10/1 = (20*V2)/2
rearrange and you get E (they don't give you an actual temperature, but since T2 is double T1, you can just use 1 and 2 since you don't need to calculate an actual number

for the second one, determine the rate with respect to B first. you'll see that from trial 1 to 2, A stays the same and B is doubled, which makes the rate X4, so rate is 2nd with respect to B. now when you look at trial 2 to 3, you see that B has doubled so you automatically know rate will be X4 which is confirmed when you look over at the rate from 2 to 3. however, you had also doubled A from 2 to 3. since rate only increased X4, you know A had no affect so the order must be 0 for A

Perfect explanation. Kaplan did a terrible job explaining