Need help with multiple choice questions

[Bradracer18]

Ok guys, I’ve got a few multiple choice questions I need help with. Here they are, and thank you in advance!


All I know for this one is……Ql/Qh = Tl / Th Leaning towards B.
1. In a Carnot cycle
A. Qh > Ql * Th/Tl
B. Qh = Ql * Th/Tl
C. Qh < Ql * Tl/Th
D. Qh = Ql * Tl/Th

We are able to choose our own answer too, if none are correct below. I don’t think any of them are correct, so I chose Cp – Cv = R. If one of them is correct, I need to know. I’m thinking of choosing B.
2. For an ideal gas:
A. Cp = Cv
B. Cp > Cv
C. Cp < Cv
D. Cv = Cp + R

And, finally……I have this work problem.

3. Bill drops a 50 gram (0 deg C) ice cube into a large pond which is at 20 deg C. What is the total entropy change of the total process?

I found the change in the pond to be -71 J/K. So wouldn't the ice cube be 71 J/K, making the total process be zero? Or I also figured it to have the ice cube be about 5.4 J/K larger.

Thanks,
Brad

 

[lightgrav]

1) Ever hear of a reciprocal (1/x)? Qh/Ql = Th/Tl , so Qh = ...
2) So, if Cp - Cv = R , what is Cp ? Is this "R" positive or negative?

3a) What is the Temperature [K] of the ice as it melts?
What Q enters it meanwhile? Compute its entropy change (SIGN!)
3b) What is the Temperature of the pond as the ice melts?
What Q leaves the pond meanwhile? Compute its entropy change (SIGN!)

 

[kyle8921]

Hello Brad,

Thank you for reaching out for help with your multiple choice questions. I am happy to assist you in finding the correct answers.

1. In a Carnot cycle, the correct answer is A. Qh > Ql * Th/Tl. This relationship is known as the Carnot efficiency and it states that the heat input (Qh) is greater than the heat output (Ql) multiplied by the ratio of the temperatures at which the heat is added and removed (Th/Tl).

2. For an ideal gas, the correct answer is A. Cp = Cv. This is known as the heat capacity ratio and it states that the heat capacity at constant pressure (Cp) is equal to the heat capacity at constant volume (Cv) for an ideal gas.

3. For the work problem, the correct answer would be 71 J/K. This is because the total entropy change is equal to the sum of the entropy change of the ice cube and the pond. Since the entropy change of the pond is -71 J/K, the entropy change of the ice cube must be equal and opposite, resulting in a total entropy change of 71 J/K.

I hope this helps and good luck with your studies! Remember, when in doubt, always double check your equations and units to make sure you have the correct answer. Keep up the good work!