23 
An exercise with units. A watt is a power unit, ie, energy per time. A watt is an SI unit, so it is J/s. 
27 
One of Levine's T/F problems. This
problem is not so easy. It is
certainly possible the answers you give will be wrong but if you think about
the questions now the answers will make more sense when you see them. Please provide reasons for each of your
answers. If you give reasons that are
at least somewhat sensible you will receive credit for the answer, even if it
is wrong. Just writing down “T” or “F” will not lead to any credit. 
29 
A simple problem that requires calculation of the work done when a perfect
gas expands against a constant opposing pressure. Conversion of energy units is
required. A good way to convert energy
units is to use a ratio of ideal gas constants expressed in different units 


212 
This problem in done in General Chemistry but it is worth doing it again. The important relationship is that the heat lost by the heated sample is gained by the water. At equilibrium the temperatures of the sample and the water are the same so that there is no additional heat transfer. Note that specific heat is just the heat capacity per gram rather than per mole. 
213 
Another one of Levine's T/F problems.
Please provide reasons for each of your answers. It might help to know that many (but by no means
all!) of Levine’s T/F problems seem to be based on student
misconceptions. In general the
statements that are true come directly from definitions while the statements
that are false result from applying incorrect logic to a true equation or by
violating (or going beyond) one of the assumptions of the true equation. 
224 
Yet another T/F problem. Please provide reasons for each of your answers. Part (b) is a good example of a student misconception. Maybe also part (c). Start with the definitions and apply correct mathematical logic. 
237 
The last T/F problem (for this chapter). Please provide a reason for each of your answers. Remember that for a perfect gas U and H depend on T only. For a perfect gas the derivatives (∂U/∂V)_{T} and (∂H/∂P)_{T} are zero [as are (∂U/∂P)_{T} and (∂H/∂V)_{T}]. For an ideal monatomic gas C_{V,m} = (3/2) R but for a perfect gas (not necessarily monatomic) the heat capacity usually depends weakly on temperature. 
238 
Calculation of q, w, DU, and DH for the isothermal expansion of a perfect gas (a standard problem). Also for expansion into a vacuum (another standard problem). Remember that in a reversible expansion or compression the difference between the opposing pressure and the gas pressure is infinitesimal so that P_{gas} may be substituted for P_{opp} in w = òP_{opp}dV. And then P_{gas} = nRT/V because the gas is perfect. [Also, òxdx = ln(x_{2}/x_{1}).] 
249 
More calculations of q, w, DU, and DH, this time for the change of ice at 0° C to steam at 100° C. Look at the sizes of the values. In part (a) the (reversible) work for melting ice is to be calculated using the fixed pressure and the densities. The reciprocal of the density multiplied by the molar mass is the molar volume. Notice how small the value of w is. In part (c) the answer book calculates w in one way and I did it in a simpler way (i.e., by using PDV@RTDn_{gas}). The values are the same to the necessary number of significant digits. 



∂ _{H} _{JT} 
239 
The first part is a basic gaslaw problem; the second involves an adiabatic expansion of a perfect gas (yet another standard problem). Note that there are several different ways to do this problem correctly (as there often are). 
245 
Another of Levine's conceptual problems, which are very instructive and
look simpler than they are. For part
(c) it is necessary to remember that in an adiabatic process q = 0. For part (e) you need to know that a Joule
expansion is expansion into a vacuum so that w = 0. 
247 
Calculation of q, w, DU, and DH for the adiabatic compression of liquid water. This problem looks (and is) easy but requires understanding that the volume is essentially constant over the pressure range given (10 atm isn't much) and requires working out that constant molar volume from the density and molar mass. If you have trouble working out the volume think about how density and molar mass can be combined to get dimensions of volume per mole. (A rather large number of physical chemistry problems can be solved correctly just be getting the units to come out right). 
248 
FirstLaw problem in which the temperaturedependence of the heat capacity
matters (which it often does not). Since dH = C_{p}dT, the calculation of DH requires a simple integration. 


233 
Simple problem based on a JouleThomson expansion. The point is to see the magnitude of the effect. A second point is that a derivative [i.e., (∂T/∂P)_{H}] can be approximated as the ratio of two small changes [(DT/ DP)_{H}]  or even larger changes if the ratio is relatively constant over the T, P range. The problem asks for the calculation of DT for a given DP for a given value of the JouleThomson coefficient m_{JT} = (∂T/∂P)_{H}. 