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Osukuuni Practice Questions
CHEM 1211
Thermochemistry
1. Classify the following processes as exothermic or endothermic:
(a) freezing of water
(b) melting of ice
(c) boiling of water
(d) heating with a
furnace
(a) exothermic
(b) endothermic
(c) endothermic
(d) exothermic
2. Is the specific heat of a substance intensive or extensive property? Explain
Specific heat capacity is J/g.K. It is constant for any given substance and does not depend
on the amount of substance, hence intensive property.
Note that heat capacity (J/K), on the other hand, depends on the mass of substance and is
extensive (heat capacity = mass x specific heat capacity)
3. Calculate q when 0.20 g of ice is cooled from 10
o
C to 75
o
C (C
ice
= 2.087 J/g.K).
q = C
s
x m x
∆
T
= (2.087 J/g.K) x (0.20 g) x (75  10) = 35 J
4. A 325g aluminum engine part at an initial temperature of 3.00
o
C absorbs 85.0 kJ of
heat. What is the final temperature of the part (C
Al
= 0.900 J/g.K)?
q = C
s
x m x
∆
T
(
29
(
29
C
3.00
T
x
g)
(325
x
J/g.K
0.900
kJ
1
J
1000
x
kJ
85
o
2

=
T
2
= 294
o
C
5. One piece of copper jewelry at 120
o
C has exactly twice the mass of another piece,
which is at 52
o
C. Find the final temperature inside the calorimeter if both pieces are
placed in the calorimeter. (Assume calorimeter has negligible heat capacity; C
copper
=
0.387 J/g.K)
If mass of copper at 52
o
C = m, then mass of copper at 120
o
C = 2m
q
hot
=  (q
cold
+ q
cal
)
q
hot copper
= C
s
x m x
∆
T = C
s
x 2m x (T
2
 120
o
C)
q
cold copper
= C
s
x m x
∆
T = C
s
x m x (T
2
 52
o
C)
Negligible heat capacity of calorimeter implies q
cal
= 0 and q
hot
=  q
cold
C
s
x 2m x (T
2
 120
o
C) =  [C
s
x m x (T
2
 52
o
C)]
C
s
and m are found on both sides so they cancel
2 x (T
2
 120
o
C) =  (T
2
 52
o
C)
T
2
= 97
o
C
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View Full Document6. An unknown volume of water at 18.2
o
C is added to 24.4 mL of water at 35.0
o
C. If the
final temperature is 23.5
o
C, what is the unknown volume? (Assume that no heat is lost to
the surroundings; density of water is 1.00 g/ml)
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 '08
 ROBERTPARSON
 Chemistry, Thermochemistry

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