9. Which of the following substances has the lowest standard molar entropy (
S
°) at 25°C?
a.
CH
3
OH(
l
)
b.
CO(
g
)
c.
MgO(
s
)
d.
H
2
O
(l)
e.
CaCO
3
(
s
)
10. When crystalline solid barium hydroxide octahydrate and crystalline solid ammonium
nitrate are mixed in a beaker at room temperature, a spontaneous reaction occurs. The
temperature of the beaker contents rapidly falls to below 0º C. Use this information to
decide whether the reaction is exothermic or endothermic and what the signs of
Δ
H and
Δ
S are.
a.
endothermic;
Δ
H > 0;
Δ
S > 0
b.
exothermic;
Δ
H < 0;
Δ
S > 0
c.
endothermic;
Δ
H < 0;
Δ
S < 0
d.
endothermic;
Δ
H < 0;
Δ
S > 0
e.
exothermic;
Δ
H > 0;
Δ
S < 0
11. Sodium carbonate can be made by heating sodium hydrogen carbonate:
2NaHCO
3
(
s
)
→
Na
2
CO
3
(
s
) + CO
2
(
g
) + H
2
O(
g
)
For this reaction,
Δ
H
° = 128.9 kJ and
Δ
S
° = 321 J/K. At approximately what temperature
will
K
= 1?
a.
401.6 K
b.
401.6º C
c.
33.1 K
d.
33.1º C
e.
none of the above
Rate Processes in Chemical Reactions—Kinetics and Equilibrium
1. For the overall hypothetical reaction A + 5B
→
4C, the rate of appearance of C given
by
Δ
[C]/
Δ
t is the same as
a.
Δ
[A]/
Δ
t
b.
-(5/4)(
Δ
[B]/
Δ
t)
c.
-(4/5)(
Δ
[B]/
Δ
t)
d.
-(1/4)(
Δ
[A]/
Δ
t)
e.
none of the above.
