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Section 2: Heat in Chemical Reaction and Processes

Heat in Chemical Reactions and Processes

1.
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


A)6.5°C
B)12.9°C
C)87.1°C
D)93.5°C
2.
Chemical reactions and physical changes that absorb energy from their surroundings are __________.
A)endothermic
B)exothermic
C)isothermic
D)mesothermic
3.
In the chemical reaction between aqueous solutions of hydrochloric acid (HCl) and sodium hydroxide (NaOH), what is the chemical system?
A)HCl and water
B)NaOH and water
C)HCl + NaOH → NaCl + H2O
D)aqueous HCl and NaOH
4.
The heat content of a system at constant pressure is defined as the ___________.
A)enthalpy
B)entropy
C)work
D)heat
5.
For the reaction below, the enthalpy change is +624.7 kJ. How would you classify this reaction?
SiO2(g) + 3C(s) → SiC(s) + 2CO(g)
A)endothermic reaction, heat is lost from the system
B)endothermic reaction, heat is gained by the system
C)exothermic reaction, heat is lost from the system
D)exothermic reaction, heat is gained by the system
6.
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.
SiO2(g) + 3C(s) → SiC(s) + 2CO(g)
A)366 kJ
B)1.13 x 105 kJ
C)5.06 kJ
D)31.2 kJ
7.
How much heat energy is liberated when 11.0 grams of manganese is used in the formation of Mn2O3?
ΔHf° for Mn2O3 is -962.3 kJ/mol
A)96.3 kJ
B)192 kJ
C)289 kJ
D)460 kJ
8.
Which of the following substances has an enthalpy value of 0 at 298 K and 1 atmosphere of pressure?
A)HCl(aq)
B)Na(s)
C)NaOH(s)
D)CO2(g)
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