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Question 1: What is the sign of ΔU as the system of ideal gas goes from point A to point B on the graph? (Hint the U is function of temperature only for a perfect gas)
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A. The states And B have the same internal energy, so delta U is zero
B. The internal energy of the system increases, so delta U is positive
C. The internal energy of the system decreases, so delta U is negative
D. Delta U cannot be determined without knowing the process used (i.e., the path taken) to get form state A to state B
Question 2: How are Q and W related during the isochoric part of the overall path form state A to state D?
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A. Q provides energy output, while W equals zero
B. Both Q and W equal zero
C. Q provides energy input, while W equals zero
D. Q provides energy input, while W provides energy output
E. Q provides energy output, while W provides energy input
Question 3: How are Q and W related during the isobaric part of the overall path for state D to state B?
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A. W provides energy output, while Q provides energy input; Q is larger
B. Both W and Q provide energy input
C. Both W and Q provide energy output
D. W provides energy output, while Q provides energy input. They are equal in magnitude.
E. W provides energy output, while Q provides energy input; W is larger B
♦ Relevant knowledge
The total amount of work performed represents the total of processes that are performed by the gas. The work accomplished by isothermal processes depends on the mole count and the size of the gas. The work performed by isobaric processes is dependent on the variations in temperature of the gas.
Question 1: Which option is correct?
Because A and B have the same internal energy, delta U is also zero.
Explanation: PV = RT is the ideal gas. All terms are given their normal meanings. We can see that the PV values for A and B are the same from the plot. Therefore, T is the same in both cases. Because U is only a function T, there will not be any change to U during the process.
Question 2: Which option is correct?
Q produces energy, while W is null.
Explanation: W = -PDV, so here to go from A to D. dV is zero. This means that there is no work. PV = RT. Since P is decreasing at constant voltage, so T will decrease, and extra heat will be released.
Question 3: Which option do you prefer?
W is the energy output and Q the energy input. They are both equal in size.
Explanation: U is a state function and the value of U at A and B is equal. Q is lost when you go from A to D. Q will be gained when you go from D to B. Q will do work on the system, which will be the output.