A question on physical chemistry
Thread Content
2mol of ideal gas, its CV,m=1.5 R, from the initial state of 300kPa, 20dm3, the volume work W=() in the process of temperature increasing by 1K under constant pressure. A． 8.314JB. 0 C. 16.63JD. -16.63J I never quite understood the first law of thermodynamics when I was reading. Now there's a problem. I don’t know how to solve this problem. Can any expert give a detailed explanation?
In the process of gas constant pressure and temperature change, the non-volume work is zero, as the ideal gas volume work w=-p△V=-nR△T, so W=-2×8.314×1=-16.628J
According to the first law of thermodynamics Q=E+A because it is an isobaric process, so Q=m/MCp,m (T2-T1) Cp,m=Cv,m+RE=m/M i/2R (T2-T1) i=3 so A=2R=16.628J Please correct me if I am wrong.
W=P ring △V, because it is a constant voltage process, P ring = P system. As the temperature increases, the volume becomes larger. In fact, work is performed on the system, which is a negative value W=-P ring △V=-nR△t=-16.63J
In fact, the two algorithms above are both correct, but in 2mol of ideal gas, its CV, m=1.5 R, from the initial state of 300kPa, 20dm3, the volume work of the process of increasing the temperature by 1K under constant pressure W = (). A． 8.314JB. 0 C. 16.63JD． -16.63J In this question, whether to choose answer C or answer D mainly depends on how it is stipulated. Because the teaching materials are different, the regulations are different, so the answers you choose are different. First of all, sir, you need to see how your textbook stipulates the positive and negative issues about workmanship?
w=-p(v2-v1), so the result is negative
The system performs work externally, directly select the negative value D
The key is to understand the chapter on the First Law of Thermodynamics!
What everyone said makes sense. What I want to say is that basic issues are so critical.
It should be C. According to the first law of thermodynamics, since it does not say whether it is an isolated system, when the temperature increases, the volume work should increase. The calculated result is 16.628J.