Problems B
225
(a) Dissolving NH 3 in water
(b) The burning (or rusting) of iron to give Fe 2 O 3
(c) Combustion of liquid C 6 H 6
(d) The reaction of metallic cadmium with dilute HC1
(e) The evolution of H 2 S on mixing HC1 and Na 2 S solutions
14. The enthalpy of combustion of rhombic sulfur is -70.96 kcal/mole. The enthalpy of combustion of monoclinic sulfur is -70.88 kcal/mole. Calculate the
standard enthalpy and entropy of transition from rhombic to monoclinic sulfur.
15. Calculate the standard enthalpy and entropy of vaporization for C 2 H 5 OH at
25°C.
16. Calculate the bond energies in the following gaseous molecules: (a) NO; (b)
H 2 O; (c) NH 3 ; (d) PC1 5 .
17. The observed heat of combustion at constant volume for sucrose
(Ci 2 H 22 O 11(s) ) at 25.0°C is A£° = -1345 kcal/mole.
(a) Write the equation for the combustion reaction and calculate A//° for the
reaction.
(b) Calculate the standard enthalpy of formation of sucrose.
(c) The overall metabolism of sucrose in your body is the same as the combustion reaction in the bomb calorimeter. Calculate how much heat is
produced in your body for every teaspoon of sugar (5.2 g) you eat and
metabolize. How much for every pound of sugar you eat?
PROBLEMS B
18. Calculate the approximate specific heat of each of the following elements: (a)
Pt; (b) P; (c) Sr; (d) As; (e) Au.
19. Calculate the resultant temperature when 250 g of water at 25.0°C are mixed
with 100 g of water at 80.0°C. (Assume no heat loss to container or surroundings.)
20. Calculate the resultant temperature when 100 g of lead metal at 200.0°C are
mixed with 200 g of water at 20.0°C. (Assume no heat loss to container or
surroundings.)
21. Suppose 200 ml of water at 55.0°C, 35.0 g of ice at 0°C, and 120 g of Zn at
100.0°C are mixed. Calculate the resultant temperature, assuming no heat
loss, and using the approximate specific heat of Zn.
22. Suppose 200 ml of water at 15.0°C, 60.0 g of ice at 0°C, and 90.0 g of Cd at
125.0°C are mixed. Calculate the resultant temperature, assuming no heat
loss, and using the approximate specific heat of Cd.
23. A metal X, whose specific heat is 0.112 cal/g °C, forms an oxide whose composition is 27.90% O.
B
(a) What is the exact atomic weight of the metal?
(b) What is the formula of the oxide?
225
(a) Dissolving NH 3 in water
(b) The burning (or rusting) of iron to give Fe 2 O 3
(c) Combustion of liquid C 6 H 6
(d) The reaction of metallic cadmium with dilute HC1
(e) The evolution of H 2 S on mixing HC1 and Na 2 S solutions
14. The enthalpy of combustion of rhombic sulfur is -70.96 kcal/mole. The enthalpy of combustion of monoclinic sulfur is -70.88 kcal/mole. Calculate the
standard enthalpy and entropy of transition from rhombic to monoclinic sulfur.
15. Calculate the standard enthalpy and entropy of vaporization for C 2 H 5 OH at
25°C.
16. Calculate the bond energies in the following gaseous molecules: (a) NO; (b)
H 2 O; (c) NH 3 ; (d) PC1 5 .
17. The observed heat of combustion at constant volume for sucrose
(Ci 2 H 22 O 11(s) ) at 25.0°C is A£° = -1345 kcal/mole.
(a) Write the equation for the combustion reaction and calculate A//° for the
reaction.
(b) Calculate the standard enthalpy of formation of sucrose.
(c) The overall metabolism of sucrose in your body is the same as the combustion reaction in the bomb calorimeter. Calculate how much heat is
produced in your body for every teaspoon of sugar (5.2 g) you eat and
metabolize. How much for every pound of sugar you eat?
PROBLEMS B
18. Calculate the approximate specific heat of each of the following elements: (a)
Pt; (b) P; (c) Sr; (d) As; (e) Au.
19. Calculate the resultant temperature when 250 g of water at 25.0°C are mixed
with 100 g of water at 80.0°C. (Assume no heat loss to container or surroundings.)
20. Calculate the resultant temperature when 100 g of lead metal at 200.0°C are
mixed with 200 g of water at 20.0°C. (Assume no heat loss to container or
surroundings.)
21. Suppose 200 ml of water at 55.0°C, 35.0 g of ice at 0°C, and 120 g of Zn at
100.0°C are mixed. Calculate the resultant temperature, assuming no heat
loss, and using the approximate specific heat of Zn.
22. Suppose 200 ml of water at 15.0°C, 60.0 g of ice at 0°C, and 90.0 g of Cd at
125.0°C are mixed. Calculate the resultant temperature, assuming no heat
loss, and using the approximate specific heat of Cd.
23. A metal X, whose specific heat is 0.112 cal/g °C, forms an oxide whose composition is 27.90% O.
B
(a) What is the exact atomic weight of the metal?
(b) What is the formula of the oxide?