Energy and Chemical Change
Practice Test
1.
How much heat is evolved when 27.0 g of glucose is burned according to this equation?
C
6
H
12
O
6
+ 6O
2
→ 6CO
2
+ 6H
2
O; Δ H comb. = -2808kJ
Specific Heats of Common Substances at 298 K (25°C)
Substance
Specific heat
J/(g·°C)
Water(l)
(liquid)
4.184
Water(s)
(ice)
2.03
Water(g)
(steam)
2.01
Ethanol(l)
(grain alcohol)
2.44
Aluminum(s)
0.897
Granite(s)
0.803
Iron(s)
0.449
Lead(s)
0.129
Silver(s)
0.235
Gold(s)
0.129
a.
280 kJ
b.
421 J
c.
136 kJ
d.
421 kJ
2.
The heat content of a system at constant pressure is defined as the ___________.
a.
enthalpy
b.
entropy
c.
work
d.
heat
3.
Calculate the enthalpy for the reaction:
2ZnS(s) + 3O
2
(g) → 2ZnO (s) + 2SO
2
(g) ΔH
f
° (kJ/mol) -206.0 0 -348.3 –296.8
a.
+270.6 kJ
b.
+878.2 kJ
c.
-270.6 kJ
d.
-878.2 kJ
4.
Chemical reactions and physical changes that absorb energy from their surroundings are __________.
a.
endothermic
b.
isothermic
c.
exothermic
d.
mesothermic
5.
Calculate ΔH° for the following reaction.
Fe
3
O
4
(s) + CO(g) → 3FeO(s) + CO
2
(g) ΔH
f
°(kJ/mol) -1118 -110.5 -272 -393.5
a.
-263 kJ
b.
neg. 50 kJ
c.
54 kJ
d.
19 kJ
6.
Which of the following substances has an enthalpy value of 0 at 298 K and 1 atmosphere of pressure?
a.
NaOH(s)
b.
Na(s)
c.
HCl(aq)
d.
CO
2
(g)
7.
In the chemical reaction between aqueous solutions of hydrochloric acid (HCl) and sodium hydroxide (NaOH), what is the chemical system?
a.
HCl + NaOH → NaCl + H
2
O
b.
NaOH and water
c.
aqueous HCl and NaOH
d.
HCl and water
8.
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.
exothermic reaction, heat is lost from the system
b.
exothermic reaction, heat is gained by the system
c.
endothermic reaction, heat is gained by the system
d.
endothermic reaction, heat is lost from the system
9.
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.
copper 0.385 J/(g·°C)
b.
gold 0.129 J/(g·°C)
c.
beryllium 1.82 J/(g·°C)
d.
calcium 0.653 J/(g·°C)
10.
A process can never be spontaneous when it is _________.
a.
exothermic, and there is an increase in disorder
b.
exothermic, and there is a decrease in disorder
c.
endothermic, and there is an increase in disorder
d.
endothermic, and there is a decrease in disorder
11.
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
12.
A body in motion possesses kinetic energy because of its __________.
a.
composition
b.
position
c.
motion
d.
inertia
13.
Which of the following processes occurs with a decrease in entropy?
a.
sublimation of dry ice
b.
boiling water
c.
freezing of water
d.
dissolving salt in water
14.
If 5.0 grams of copper cools from 35.0°C to 22.6°C and loses 23.6 joules of heat, what is the specific heat of copper?
a.
0.076 J/(g·°C)
b.
3.8 ´ 102 J/(g·°C)
c.
0.38 J/(g·°C)
d.
0.62 J/(g·°C)
15.
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.
35°C
b.
30°C
c.
25°C
d.
40°C
16.
At one atmosphere pressure and the melting point of a substance, which statement is true about this general equation? solid 3 liquid
a.
ΔG = 0 for the process
b.
ΔS = 0 for the process
c.
Both ΔH and ΔS = 0 for the process
d.
ΔH = 0 for the process
17.
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.
1.14 x 104 J
b.
270 J
c.
540 J
d.
812 J
18.
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.
299 kJ
b.
-114 kJ
c.
-299 kJ
d.
114 kJ
19.
How much heat is required to melt 200 grams of ice? The heat of fusion is 333 J/g.
a.
666 J
b.
d. 6.66 kJ
c.
66.6 kJ
d.
c. 1.66 J
20.
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.
b. -376 kJ
d.
-775 kJ
21.
Calculate the ΔG° for the reaction:
2C
2
H
2
(g) + 5O
2
(g) → 4CO
2
(g) + 2H
2
O(l)ΔG° (kJ/mol)209.2, 0, -394.4, -237.2
a.
-2470 kJ
b.
-1643 kJ
c.
-2599 kJ
d.
-1409 kJ
