Gas-phase absolute entropy

Question

Assignment:

Question 1. Which molecule below should have the highest gas-phase absolute entropy at 25°C?

a. CH4
b. H2
c. C2H6
d. C2H4
e. C2H2

Question 2. Some standard entropies (at 25°C in J/mol K) are given:
Ca²⁺(aq) -55.2, F^-(aq) -9.6, CaF₂(s) +68.87. ΔS° for the reaction CaF₂(s) → Ca²⁺(aq) + 2F^-(aq) at 25°C in J/K is __________.

a. -5.5
b. -133.7
c. +133.7
d. -143.3
e. +143.3

Question 3. Given the following table of thermodynamic data,
substance    S°

C₂H₂ (g)    200.8 J/mol ^{- K}
C₂H₄ (g)    219.4
C₂H₆ (g)    229.5
H₂ (g)    130.58

determine the ΔS° (in J/mol ^-K) for the reaction:

C₂H₂ (g) + H₂ (g) → C₂H₄ (g)

a. -232.46
b. +111.98
c. +101.88
d. -101.88
e. -111.98

Question 4. The standard free energy of formation of __________ is zero.

a. O (g)
b. H₂O (l)
c. N₂ (g) and O (g)
d. N₂ (g)
e. Br₂ (s)

Question 5. Consider the following table of thermodynamic data. All values are tabulated for 25°C.
Substance    ΔG°f (kJ/mol)    S° (J/mol ? K)

C₂H₂ (g)    209    201
C₂H₄ (g)    68    219
C₂H₆ (g)    -33    230
H₂ (g)           0    131
H₂O (g)      -229    189
C₂H₅OH (l)  -175    161

Question 6. What is the value of ΔH° (in kJ) for the reaction described below? Assume the reaction is performed at 25°C.

C₂H₂ (g) + 2H₂ (g) → C₂H₆ (g)

a. -173
b. -248
c. -311
d. 149
e. 236