9.14
EXERCISES 1.
What are the signs of
HΔ
o and
SΔ
o for the evaporation of water?
- What are the signs of
HΔ
o and
SΔ
o for cooling liquid water?
- A system gives off 600 J of heat while 200 J of work are done on it. What
are
E, Δ
EΔ
sur
, and
EΔ
univ
?
- A system does 400 J of work and absorbs 150 J of heat. What are
E, Δ
EΔ
(^) sur
and
EΔ
univ
?
- What is the difference between
H and Δ
E? Why is Δ
H used more Δ
frequently by chemists than
E? Δ
- What are the standard states of a gas and a solute? 7. When is the entropy change of a
reaction expected to be significant?
8.
Indicate whether each of the following
is true, false, or cannot be
determined for a non-extensive reaction at constant pressure and temperature that is proceeding spon
taneously to consume gas molecules.
a)
G < 0 Δ
b)
SΔ
o ~ 0
c)
GΔ
o < 0
d)
EΔ
univ
= 0
e)
HΔ
o < 0
f) the extent of reaction increases with T
9.
Indicate whether each of the following
is true, false, or cannot be
determined for an extensive endothermic reaction that is at equilibrium at constant pressure and temperature.
a)
G < 0 Δ
b)
HΔ
o < 0
c)
GΔ
o < 0
d)
SΔ
univ
> 0
e)
SΔ
o > 0
f) the extent of reaction increases with T
10.
The enthalpy of combustion of propane gas, C
H 3
(g), is -2,220 kJ/mol. 8
a) Write the balanced equation for the combustion reaction. b) Propane is often used for gas grills, which usually have a propane tank
with 20 pounds of propane. How much heat can be obtained by burning all of the propane in a 20 lb tank? (1 lb = 454 g)
c) What is the enthalpy change for 6CO
(g) + 8H 2
O(l) 2
→
2C
H 3
(g) + 8
10O
(g)? 2
11.
Combustion of 0.150 g of C
H 2
OH(l) (grain alcohol) 5
releases 4.47 kJ of
heat.
a) What is the enthalpy of combustion of C
H 2
OH(l)? 5
b)
Write the chemical equation for the combustion reaction.
c) What is
ΔH
o for 4CO
(g) + 6H 2
O(l) 2
→
2C
H 2
OH(l) + 6O 5
(g)? 2
12.
Use the data in Table 9.2 to estimate the enthalpies of the following reactions: a)
H
CBr 2
(g) + F 2
(g) 2
→
H
CF 2
(g) + Br 2
(g) 2
b) H
CI(g) + H 3
O(g) 2
→
H
COH(g) + HI(g) 3
c) HC
≡CH(g) + 2H
(g) 2
→
H
C-CH 3
(g) 3
d) CH
(g) 4
→
C(g) + 2H
(g) 2
13.
Use Table 9.2 to estimate the enthalpies of the following reactions: a)
H
C=CH 2
(g) + 3O 2
(g) 2
→
2CO
(g) + 2H 2
O(g) 2
b) 4CH
NH 3
(g) + 9O 2
(g) 2
→
4CO
(g) + 10H 2
O(g) + 2N 2
(g) 2
c) CCl
(g) + O 4
(g) 2
→
CO
(g) + 2Cl 2
(g) 2
d) 4HC
≡N(g) + 5O
(g) 2
→
4CO
(g) + 2H 2
O(g) + 2N 2
(g) 2
14.
Indicate
ΔS
o > 0,
ΔS
o ~ 0, or
ΔS
o < 0 for each of the following reactions:
a) 2H
(g) + O 2
(g) 2
→
2H
O(l) 2
b) HF(aq) + NO
1-(aq) 2
→
1- F
(aq) + HNO
(aq) 2
c) H
(g) + I 2
(g) 2
→
2HI(g)
d) CaCO
(s) 3
→
CaO(s) + CO
(g) 2
15.
Indicate
ΔS
o > 0,
ΔS
o ~ 0, or
ΔS
o < 0 for each of the following reactions:
a) H
CI(aq) + OH 3
1-(aq)
→
H
COH(aq) + I 3
1-(aq)
b) CCl
(l) 4
→
CCl
(g) 4
c) C
H 2
(g) + 2H 2
(g) 2
→
C
H 2
(g) 6
d) H
(g) + CO 2
(g) 2
→
H
O(g) + CO(g) 2
16.
Indicate the sign of
ΔG
o at low and high temperatures for each of the
following processes: a) NH
(g) + HCl(g) 3
→
NH
Cl(s) 4
Δ
oH
< 0
b) CaCO
(s) 3
→
CaO(s) + CO
(g) 2
Δ
oH
> 0
c) CH
OH(l) 3
→
CH
OH(g) 3
ΔH
o > 0
d) 2Cl
(g) + 7O 2
(g) 2
→
2Cl
O 2
(l) 7
ΔH
o > 0
Chapter 9 Reaction Energetics
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