Section 16.2
Heat in Chemical Reactions and Processes
Practice Test
1.
How much heat is absorbed in the complete reaction of 3.00 grams of SiO2 with excess carbon in the reaction below? ΔH° for the reaction is +624.7 kJ.
SiO
2
g
+ 3C
s
→ SiC
s
+2CO
g
SC.A.1.4.5
a.
1.13 ´ 105 kJ
b.
5.06 kJ
c.
31.2 kJ
d.
366 kJ
Hint
2.
In the chemical reaction between aqueous solutions of hydrochloric acid
HCl
and sodium hydroxide
NaOH
, what is the chemical system?
a.
NaOH and water
b.
HCl and water
c.
aqueous HCl and NaOH
d.
HCl + NaOH → NaCl + H
2
O
Hint
3.
How much heat energy is liberated when 11.0 grams of manganese is used in the formation of Mn
2
O
3
?
ΔH
f
° for Mn
2
O
3
is -962.3 kJ/mol
SC.1.4.5
a.
192 kJ
b.
96.3 kJ
c.
289 kJ
d.
460 kJ
Hint
4.
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 gained by the system
b.
endothermic reaction, heat is lost from the system
c.
exothermic reaction, heat is lost from the system
d.
exothermic reaction, heat is gained by the system
Hint
5.
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.
CO
2
g
d.
HCl
aq
Hint
6.
The heat content of a system at constant pressure is defined as the ___________.
a.
enthalpy
b.
work
c.
entropy
d.
heat
Hint
7.
Chemical reactions and physical changes that absorb energy from their surroundings are __________.
a.
endothermic
b.
mesothermic
c.
isothermic
d.
exothermic
Hint
8.
If 500 g of water at 100°C loses 27,000 J of heat, what is the final temperature of the water?
Specific Heats of Common Substances at 298 K
25°C
Specific heat
Substance 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
SC.B.1.4.2
a.
6.5°C
b.
93.5°C
c.
12.9°C
d.
87.1°C
Hint
