Chapter 16:
Energy and Chemical Change
Practice Test
1.
Which of the following occurs with an increase in entropy?
a.
twenty nickels taken from a box and arranged tails up on a table
b.
the reaction PCl
3
(g) + Cl
2
(g) → PCl
5
(g)
c.
precipitation of silver chloride from a solution of silver ions and chloride ions
d.
evaporation of carbon tetrachloride
Hint
2.
Given the following information,
SO
3
(g) + H
2
O(l) → H
2
SO
4
(l) Δ
H
° = -133 kJ
Pb(s) + PbO
2
(s) + 2H
2
SO
4
(l) → 2PbSO
4
(s) + 2H
2
O(l) Δ
H
° = -509 kJ
calculate the Δ
H
° for the reaction below.
Pb(s) + PbO
2
(s) + 2SO
3
(g) → 2PbSO
4
(s)
a.
+376 kJ
b.
-642 kJ
c.
-376 kJ
d.
-775 kJ
Hint
3.
Calculate the enthalpy for the reaction below
2ZnS(s) + 3O
2
(g) → 2ZnO(s) + 2SO
2
(g)
Δ
H
f
° (kJ/mol) -206.0 0 -348.3 -296.8
a.
-878.2 kJ
b.
-270.6 kJ
c.
+270.6 kJ
d.
+878.2 kJ
Hint
4.
Calculate Δ
H
° for the following reaction.
Fe
3
O
4
(s) + CO(g) → 3FeO(s) + CO
2
(g)
Δ
H
° (kJ/mol) -1118 -110.5 -272 -393.5
a.
-50 kJ
b.
54 kJ
c.
-263 kJ
d.
19 kJ
Hint
5.
From the following data,
H
2
(g) + Cl
2
(g) → 2HCl(g) Δ
H
°v = -185 kJ
2H
2
(g) + O
2
(g) → 2H
2
O(g) Δ
H
° = -483.7 kJ
calculate Δ
H
° for the following reaction.
4HCl(g) + O
2
(g) → 2Cl
2
(g) + 2H
2
O(g)
a.
-114 kJ
b.
-299 kJ
c.
+299 kJ
d.
+114 kJ
Hint
6.
For the reaction below, the enthalpy change is +624.7 kJ. How would you classify this reaction?
SiO
2
(g) + 3C(s) → SiC(s) + 2CO(g)
a.
endothermic reaction, heat is lost from the system
b.
exothermic reaction, heat is gained by the system
c.
exothermic reaction, heat is lost from the system
d.
endothermic reaction, heat is gained by the system
Hint
7.
How much heat is required to melt 200 grams of ice? The heat of fusion is 333 J/g.
a.
1.66 J
b.
6.66 kJ
c.
66.6 kJ
d.
666 J
Hint
8.
Which of the following processes occurs with a decrease in entropy?
a.
sublimation of dry ice
b.
dissolving salt in water
c.
boiling water
d.
freezing of water
Hint
9.
Calculate the amount of heat absorbed by 10.0 grams of ice at -15.0°C as it is converted to liquid water at 50.0°C. The specific heat of H
2
O(s) = 2.09 J/(g•°C). The specific heat of H
2
O(l) = 4.18 J/(g•°C). The heat of fusion is 333 J/g.
a.
0.170 kJ
b.
5.73 kJ
c.
2.83 kJ
d.
0.676 kJ
Hint
10.
Which of the following substances has an enthalpy value of 0 at 298 K and 1 atmosphere of pressure?
a.
CO
2
(g)
b.
NaOH(s)
c.
Na(s)
d.
HCl(aq)
Hint
11.
The heat content of a system at constant pressure is defined as the ___________.
a.
enthalpy
b.
entropy
c.
heat
d.
work
Hint
12.
Calculate the Δ
G
° for the reaction below.
2C
2
H
2
(g) + 5O
2
(g) → 4CO
2
(g) + 2H
2
O(l)
Δ
G
° (kJ/mol) 209.2 0 -394.4 -237.2
a.
-2599 kJ
b.
-1643 kJ
c.
-2470 kJ
d.
-1409 kJ
Hint
13.
Calculate the entropy change for the reaction below.
N
2
(g) + 3H
2
(g) → 2NH
3
(g)
S
° (J/mol•K) 191.5 130.6 192.3
a.
-198.7 J/K
b.
76.32 J/K
c.
-129.7 J/K
d.
303.2 J/K
Hint
14.
At one atmosphere pressure and the melting point of a substance, which statement is true about this general equation?
solid 3 liquid
a.
Δ
S
= 0 for the process
b.
Δ
G
= 0 for the process
c.
Both Δ
H
and Δ
S
= 0 for the process
d.
Δ
H
= 0 for the process
Hint
15.
In the chemical reaction between aqueous solutions of hydrochloric acid (HCl) and sodium hydroxide (NaOH), what is the chemical system?
a.
aqueous HCl and NaOH
b.
HCl and water
c.
NaOH and water
d.
HCl + NaOH → NaCl + H
2
O
Hint
16.
What is the final temperature of a mixture of chromium metal and water when 50.0 grams of chromium at 15°C (specific heat = 0.448 J/(g•°C)) is added to 25 mL of water (specific heat = 4.18 J/(g•°C)) at 45°C? The density of water is 1 g/mL.
a.
40°C
b.
25°C
c.
30°C
d.
35°C
Hint
17.
Calculate the free energy for the following reaction at 25°C.
2ZnS(s) + 3O
2
(g) → 2ZnO(s) + 2SO
2
(g)
Δ
H
° (kJ/mol) -205.6 0 -348.3 -296.8
Δ
S
° v(J/mol•K) 57.5 205.0 43.64 248.1
a.
-704.2 kJ
b.
-922.6 kJ
c.
-835 kJ
d.
-951.1 kJ
Hint
18.
The same amount of heat is added to a 10-g sample of each of the following metals. If each metal is initially at 20.0°C, which metal will reach the highest temperature?
a.
gold 0.129 J/(g•°C)
b.
calcium 0.653 J/(g•°C)
c.
beryllium 1.82 J/(g•°C)
d.
copper 0.385 J/(g•°C)
Hint
19.
A process can never be spontaneous when it is _________.
a.
exothermic, and there is an increase in disorder
b.
endothermic, and there is a decrease in disorder
c.
exothermic, and there is an increase in disorder
d.
endothermic, and there is an increase in disorder
Hint
20.
The specific heat of aluminum is 0.900 J/(g•°C). How many joules of heat are absorbed by 30.0 g of aluminum if it is heated from 20.0°C to 40.0°C?
a.
540 J
b.
270 J
c.
1.14 × 10
4
J
d.
812 J
Hint
