Physical Chemistry Answers

Which of the following reactions has the largest positive value of ΔS per mole of O2?

A) 2C(s) + O2(g) → 2CO(g)
B) 2NO(g) + O2(g) → 2NO2(g)
C) 2Mg(s) + O2(g) → MgO(s)
D) 2H2(g) + O2(g) → 2H2O(g)
E) C(s) + O2(g) → CO2(g)

Which of the following processes would be expected to have a positive ΔS value?

A) 2NO(g) + O2(g) = 2NO2(g)
B) Cl2(g) + Br2(g) = 2ClBr(g)
C) N2(g) + 3H2(g) =
D) 2NH3(g)
E) H2O(l) = H2O(s)
CaCO3(s) = CaO(s) + CO2(g)

Which of the following has the lowest value of absolute entropy per mole? Conditions are as defined in each case.


A) solid sodium at 30 oC
B) gaseous sodium at 900 oC and 0.5 atm
C) gaseous sodium at 900 oC and 1 atm
D) liquid sodium at 100 oC
E) a solid solution of sodium in potassium at 30oC

All of the following have values of zero for free energy of formation, except:

A) Fe(l)
B) S8(s)
C)N2(g)
D)Br2(l)
E) Hg(l)

Using tabulated thermodynamic data, the value of ΔS° for the oxidation of carbon to carbon monoxide, 2C (s, graphite) + O2 (g) → 2CO (g) is __________ J/K.

A) -12.8
B) +179.4
C) +395.8
D) +408.6
E) -408.6

Which of the following statements is false?


A) The change in entropy in a system depends on the initial and final states of the system and the path taken from one state to the other.
B) Any irreversible process results in an overall increase in entropy.
C) The total entropy of the universe increases in any spontaneous process.
D)Entropy increases with the number of microstates of the system.

Which one of the following processes produces a decrease in the entropy of the system?

A) melting ice to form water
B) boiling water to form steam
C) freezing water to form ice
D) dissolution of solid KCl in water
E) mixing of two gases into one container

The reaction

CH4(g) + N2(g) = HCN(g) + NH3(g)

at 25 oC and 1 atm pressure has
ΔHo = 164 kJ and
ΔGo = 159 kJ. Calculate
ΔSo at 25 oC.


A) 400 J/K
B) 100 J/K
C) 2 J/K
D) 17 J/K
E) 70 J/K

For a reaction system which is at equilibrium, which of the following must always be true?

A) q = 0
B) ΔH = 0
C) ΔS = 0
D) ΔU = 0
E) ΔG = 0

For the reaction
4Ag(s) + O2(g) = 2Ag2O(s) at 25 oC and 1 atm pressure,
ΔHo is -61140 J andΔSo is 132 J/K.
Assuming that ΔHo and ΔSo are essentially temperature independent, which of the following statements is true?



A) The reaction will not be spontaneous at any
temperature.

B) The reaction will be spontaneous at all
temperatures.

C) The reaction will be spontaneous at low temperatures,
and the reverse reaction will be spontaneous at high
temperatures.

D) The reaction will be spontaneous at high temperatures,
and the reverse reaction will be spontaneous at low
temperatures.

E) The change in entropy is the driving force at low
temperatures.