City Colleges of Chicago Physical Chemistry for Biochemists Questions

Chemistry 340 Physical Chemistry for Biochemists IFall 2022
HOMEWORK SET No. 3
This homework set is due on Friday, September 16, 2022
1. How high can a person (assume a weight of 70 kg) climb on one ounce of chocolate, if
the heat of combustion (628 kJ) can be converted completely into work of vertical
displacement?
2. A mole of sodium metal is added to water. How much work is done on the atmosphere
by the subsequent reaction if the temperature is 25 °C?
3. Show that the function defined by df ( x, y ) =
( y 2 − xy ) dx − x 2 dy is inexact. Test the
4.
5.
6.
7.
8.
integrating factor 1/ xy 2 to see whether it produces an exact differential.
An ideal gas is expanded reversibly and isothermally from 10 bar to 1 bar at 298.15 K.
What are the values of (a) w per mole, (b) q per mole, (c) ∆U , and (d) ∆H . (e) If the ideal
gas expands isothermally against a constant pressure of 1 bar, how much work is done on
the gas?
Calculate the temperature increase and final pressure of helium if a mole is compressed
adiabatically and reversibly from 44.8 L at 0 °C to 22.4 L.
A mole of argon is allowed to expand adiabatically and reversibly from a pressure of 10
bar and 298.15 K to 1 bar. What is the final temperature, and how much work is done on
the argon?
Calculate H °(2000 K) − H °(0 K) for H(g).
For a diatomic molecule the bond energy is equal to the change in internal energy for the
reaction
X 2 ( g) = 2X(g)
at 0 K. Of course, the change in internal energy and the change in enthalpy are the same
at 0 K. Calculate the enthalpy of dissociation of O2(g) at 0 K. The enthalpy of formation of
O(g) at 298.15 K is 249.173 kJ mol−1. In the range 0-298 K the average value of the heat
capacity of O2(g) is 29.1 J K −1 mol−1 and the average value of the heat capacity of O(g) is
22.7 J K −1 mol−1. What is the value of the bond energy in electron volts? (When the
changes in heat capacities in the range 0-298 K are considered, the enthalpy of
dissociation at 0 K is 493.58 kJ mol−1. )
9. The heat capacity of a gas may be represented by Cp =α + β T + γ T 2
−1
For N=
26.984 J K −1 mol=
, β 5.910 ×10−3 J K −2 mol−1 , and
2 α
γ=
−3.377 ×10−7 J K −3 mol−1. How much heat is required to heat a mole of N2 from 300 K
to 1000 K?