Comments re Chapter 3 Problems:
|
3-8 |
A set of T/F questions about entropy. The most difficult is probably (a). Note that it is not specified whether the S under discussion applies to the system or the universe; assume then that S is for the system. It helps to know that reversible and irreversible paths that connect the same initial and final states of the system usually do not connect the same initial and final states of the surroundings. |
|
3-15 |
Calculation of DS for an irreversible phase change that is carried out isothermally. It is necessary to find a reversible path that connects the initial and final states. This is a classic problem that should be understood thoroughly. |
|
3-17 |
Calculation of DS for an irreversible process that is carried out adiabatically. Remember that the cooling of the Au and the heating of the water are not carried out reversibly but could be carried out reversibly. Before DS for either substance can be calculated the final temperature must be determined, but that is a type of problem covered in CHE105/107. |
|
3-19 |
A calculation of DS for the mixing of two gases. The equation was derived using Pv=nRT but applies to mixing problems involving solids and liquids as well. This kind of calculation is quite often used inappropriately. The number of moles is the number of moles of objects (here, gas molecules) that are mixed. The DS for mixing a cup of solid table salt and a cup of table sugar is too small to measure because the number of moles of the objects being mixed (salt and sugar crystals) is about 10E-16. |
|
3-21 |
Another T/F problem. |
|
3-32 |
Practice in distinguishing between reversible and irreversible processes. The key question is, can you imagine making a very minor change that would cause the process to reverse direction? |
Return
to the