'roblems A
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positive, and the reaction is endothermic; AE may be larger or smaller than A//
depending on the sign of Arc.
PROBLEMS A
1. Calculate the approximate specific heat of each of the following elements: (a)
S; (b) Zn; (c) La; (d) U; (e) Pb.
2. Calculate the resultant temperature when 150 g of water at 75.0°C is mixed
with 75.0 g of water at 20.0°C. (Assume no heat loss to container or surroundings.)
3. Calculate the resultant temperature when 50.0 g of silver metal at 150.0°C is
mixed with 50.0 g of water at 20.0°C. (Assume no heat loss to container or
surroundings.)
4. Suppose 150 ml of water at 50.0°C, 25.0 g of ice at 0°C, and 100 g of Cu at
100.0°C are mixed together. Calculate the resultant temperature, assuming no
heat loss, and using the approximate specific heat of Cu.
5. Suppose 150 ml of water at 20.0°C, 50.0 g of ice at 0°C, and 70.0 g of Cu at
100.0°C are mixed together. Calculate the resultant temperature, assuming no
heat loss, and using the approximate specific heat of Cu.
6. A Dewar flask (vacuum-jacketed bottle) is used as a calorimeter, and the
following data are obtained. Measurements in parts (a) and (b) are made to
obtain the heat capacity of the calorimeter, and parts (c) and (d) are performed
on an unknown metal.
(a) Calorimeter with 150.0 g of H 2 O has a temperature of 21.3°C.
(b) When 35.0 ml of H 2 O at 99.5°C are added to the calorimeter and water of
part (a), the resultant temperature is 35.6°C.
(c) Calorimeter with 150.0 g of H 2 O has a temperature of 22.7°C.
(d) A 50.3 g sample of metal at 99.5°C added to the calorimeter and water of
(c) gives a resultant temperature of 24.3°C.
Calculate the approximate atomic weight of the metal.
7. A 100.0 g sample of glycerol is put into the calorimeter calibrated in Problem
6, and its temperature is observed to be 20.5°C. Then 45.7 g of iron at 165.0°C
are added to the glycerol, giving a resultant temperature of 37.4°C. Calculate
the specific heat of the glycerol. (Use the approximate specific heat of iron.)
8. Calculate the heat capacity of a calorimeter (Figure 14-1) that, when containing 300 ml of water, requires a current of 0.840 amp passing for 3 min 41 sec
through a 9.05 ohm immersed resistance in order to raise the water temperature from 22.376°C to 23.363°C.
9. Calculate the following quantities, using the calorimeter calibrated in Problem
8.
(a) The specific heat of a water-insoluble material. First, 38.5 g of a finely
divided sample are stirred with 250 ml of water; then a current of 0.695
223
positive, and the reaction is endothermic; AE may be larger or smaller than A//
depending on the sign of Arc.
PROBLEMS A
1. Calculate the approximate specific heat of each of the following elements: (a)
S; (b) Zn; (c) La; (d) U; (e) Pb.
2. Calculate the resultant temperature when 150 g of water at 75.0°C is mixed
with 75.0 g of water at 20.0°C. (Assume no heat loss to container or surroundings.)
3. Calculate the resultant temperature when 50.0 g of silver metal at 150.0°C is
mixed with 50.0 g of water at 20.0°C. (Assume no heat loss to container or
surroundings.)
4. Suppose 150 ml of water at 50.0°C, 25.0 g of ice at 0°C, and 100 g of Cu at
100.0°C are mixed together. Calculate the resultant temperature, assuming no
heat loss, and using the approximate specific heat of Cu.
5. Suppose 150 ml of water at 20.0°C, 50.0 g of ice at 0°C, and 70.0 g of Cu at
100.0°C are mixed together. Calculate the resultant temperature, assuming no
heat loss, and using the approximate specific heat of Cu.
6. A Dewar flask (vacuum-jacketed bottle) is used as a calorimeter, and the
following data are obtained. Measurements in parts (a) and (b) are made to
obtain the heat capacity of the calorimeter, and parts (c) and (d) are performed
on an unknown metal.
(a) Calorimeter with 150.0 g of H 2 O has a temperature of 21.3°C.
(b) When 35.0 ml of H 2 O at 99.5°C are added to the calorimeter and water of
part (a), the resultant temperature is 35.6°C.
(c) Calorimeter with 150.0 g of H 2 O has a temperature of 22.7°C.
(d) A 50.3 g sample of metal at 99.5°C added to the calorimeter and water of
(c) gives a resultant temperature of 24.3°C.
Calculate the approximate atomic weight of the metal.
7. A 100.0 g sample of glycerol is put into the calorimeter calibrated in Problem
6, and its temperature is observed to be 20.5°C. Then 45.7 g of iron at 165.0°C
are added to the glycerol, giving a resultant temperature of 37.4°C. Calculate
the specific heat of the glycerol. (Use the approximate specific heat of iron.)
8. Calculate the heat capacity of a calorimeter (Figure 14-1) that, when containing 300 ml of water, requires a current of 0.840 amp passing for 3 min 41 sec
through a 9.05 ohm immersed resistance in order to raise the water temperature from 22.376°C to 23.363°C.
9. Calculate the following quantities, using the calorimeter calibrated in Problem
8.
(a) The specific heat of a water-insoluble material. First, 38.5 g of a finely
divided sample are stirred with 250 ml of water; then a current of 0.695