Error on question 69 from Kaplan BB?

[Gauch08]

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I just did the test from the Kaplan blue book and was going over the test and have a question about 69. This problem gives you a diagram of the heat curve and I thought the answer was D but the solution said it is B because the heat of vaporization is greater than heat of fusion. Shouldn't the heat of fusion be greater since it has a longer plateau than vaporization? I'm so confused. 😱

 

[Gauch08]

I think there is an error on number 92 also. The answer choice says E but the carbonyl carbon can't have 5 bonds so it can't work. But instead, C should work. Can someone tell me if I'm right??

 

[dudewhensmydat]

I just did the test from the Kaplan blue book and was going over the test and have a question about 69. This problem gives you a diagram of the heat curve and I thought the answer was D but the solution said it is B because the heat of vaporization is greater than heat of fusion. Shouldn't the heat of fusion be greater since it has a longer plateau than vaporization? I'm so confused. 😱

Delta heat of sublimation > Delta heat of vaporization > Delta heat of fusion.

Remember:

Sublimation: solid to gas
Vaporization: liquid to gas
Fusion: solid to liquid

The heat of enthalpy for breaking bonds (a positive value of delta H) is greater for vaporization than for fusion b/c a gas is way more different than a liquid whereas solids and liquids are more siimilar.

hope this helps, dude.

 

[Gauch08]

Delta heat of sublimation > Delta heat of vaporization > Delta heat of fusion.

Remember:

Sublimation: solid to gas
Vaporization: liquid to gas
Fusion: solid to liquid

The heat of enthalpy for breaking bonds (a positive value of delta H) is greater for vaporization than for fusion b/c a gas is way more different than a liquid whereas solids and liquids are more siimilar.

hope this helps, dude.

This makes sense but the question gives you a heat diagram and looks like this.
|
|
|******************/***********
|************_____/***********
| ***********/****************
|**_________/*****************
|*/***************************
|/ ***************************
|****************************
|****************************
|____________________________
Q
Just look at the line because the * mark is there to keep the diagram to look correctly. Anyways this shows heat of fusion is bigger than heat of vaporization right since the plateau is longer for heat of fusion?

 

[dudewhensmydat]

This makes sense but the question gives you a heat diagram and looks like this.
|
|
|******************/***********
|************_____/***********
| ***********/****************
|**_________/*****************
|*/***************************
|/ ***************************
|****************************
|****************************
|____________________________
Q
Just look at the line because the * mark is there to keep the diagram to look correctly. Anyways this shows heat of fusion is bigger than heat of vaporization right since the plateau is longer for heat of fusion?

I'm quoting from the answer to the question (I took the Kaplan course)...

The answer is B b/c the "heat of vaporization requires greater magnitude of Q (heat) than the heat of fusion. The heat of fusion is the the bottom plateau while the heat of vaporization is the top plateau."

I understand your logic, but this is what the book says. It also says that one can tell by looking at the slopes, but that it wouldn't work for this diagram since all the slopes are equal. Steeper slope = less heat (Q) required to increase the temperature = lower heat capacity.

I feel your pain.

 

[Gauch08]

I'm quoting from the answer to the question (I took the Kaplan course)...

The answer is B b/c the "heat of vaporization requires greater magnitude of Q (heat) than the heat of fusion. The heat of fusion is the the bottom plateau while the heat of vaporization is the top plateau."

I understand your logic, but this is what the book says. It also says that one can tell by looking at the slopes, but that it wouldn't work for this diagram since all the slopes are equal. Steeper slope = less heat (Q) required to increase the temperature = lower heat capacity.

I feel your pain.

I guess I understand this question now. What do you think about number 92?

 

[DAS]

question 92 is not wrong because if you look closely, you will notice that the carbon in choice E has only 4 bonds not five( 2 with the ring, 1 with each oxygen). Hope that helps.
can you help me with the question I posted from the same exam.🙂

 

[Gauch08]

question 92 is not wrong because if you look closely, you will notice that the carbon in choice E has only 4 bonds not five( 2 with the ring, 1 with each oxygen). Hope that helps.
can you help me with the question I posted from the same exam.🙂

How does the carbon have only 4 bonds. It is clear that there are two bonds connected to the ring, two on the oxygen and one more on other oxygen. So carbon has 5 bonds and breaking the octet rule since carbon has no D orbital to allow 5 bonds. But answer choice C has only 4 bonds for the Carbon so shouldn't C be the right answer?

 

[DAS]

If we are looking at the same question, i.e KAPLAN final exam Q#92, then I see on choice E Carbon only has 4 bonds because it has 2 with the ring and 1 bond with each oxygen. there is no double bond with oxygen in choice E, but if you look at choice D, the carbon has a double bond with one of the ixygen molecules. look closely, or drink some coffee.🙂

 

[Gauch08]

If we are looking at the same question, i.e KAPLAN final exam Q#92, then I see on choice E Carbon only has 4 bonds because it has 2 with the ring and 1 bond with each oxygen. there is no double bond with oxygen in choice E, but if you look at choice D, the carbon has a double bond with one of the ixygen molecules. look closely, or drink some coffee.🙂

Wait you are looking at the final exam?? I'm looking at the paper test from the kaplan blue book 2006-2007. Answer E DOES have 5 bonds on the carbon and answer D has only has 4 bonds on the carbon. In fact, answer A has three bonds and BCD has 4 bonds.

Is the final the same thing as the paper test from the Blue book then? If it is what is the midterm same as?

 

[DAS]

I have no idea what the blue book is. I just got some KAPLAN materials from a friend of mine who took it last year. I have the solution to the mid term exam, but she didn't give me the test. So, I guess I have no idea what is what.