182
Stoichiometry II: Calculations Based on Chemical Equations
(a) What weight of copper and (b) how many moles of HNO 3 are needed to
prepare 500 ml NO, measured over water at 730 torr and 25°C?
(c) If the nitric acid solution contains 10.0 moles/liter, what volume of the
solution is used?
13. Arsenic compounds may be detected easily by the Marsh test. In this test,
some metallic zinc is added to an acid solution of the material to be tested, and
the mixture is heated. The arsenic is liberated as arsine, AsH 3 , which may be
decomposed by heat to give an "arsenic mirror." The reaction is
4Zn + H 3 AsO 4 + 8HC1 -^ 4ZnCl 2 + AsH 3 + 4H 2 O
What volume of AsH 3 at 720 torr and 25°C is evolved by 7.00 x 10~
7 g of
arsenic, the smallest amount of arsenic that can be detected with certainty by
this method?
14. H 2 S gas will cause immediate unconsciousness at a concentration of 1 part per
1000 by volume. What weight of FeS is needed to fill a room 20 ft x 15 ft x 9 ft
with H 2 S at this concentration? Barometric pressure is 740 torr, and the temperature is 80°F. The reaction is
FeS + 2HC1 -> FeCl 2 + H 2 S
15. The Mond process separates nickel from other metals by passing CO over the
hot metal mixture. The nickel reacts to form a volatile compound (called
nickel carbonyl), which is then swept away by the gas stream. The reaction is
Ni + 4CO -^ Ni(CO) 4
How many cubic feet of CO at 3.00 atm and 65°Fare needed to react with 1.00
ton of nickel?
16. A cement company produces 100 tons of cement per day. Its product contains
62.0% CaO, which is prepared by calcining limestone by the reaction
CaCO 3 -^ CaO + CO 2
What volume of CO 2 at 735 torr and 68°F is sent into the air around the plant
each day as a result of this calcination?
17. The Ostwald process of making HNO 3 involves the air oxidation of NH 3 over
a platinum catalyst. The first two steps in this process are
4NH 3 + 50 2 -^ 6H 2 O + 4NO
2ND + O 2 ^ 2NO 2
How many cubic feet of air (21% O 2 by volume) at 27°C and 1.00 atm are
needed for the conversion of 50.0 tons of NH 3 to NO 2 by this process?
18. How many cubic feet of air (21% O 2 by volume) are needed for the production
of 10
5 ft
3 NO 2 at the same conditions as those used to measure the air? (See
Problem 17 for the equations involved.)
19. The du Pont company has developed a nitrometer, an apparatus for the rapid
routine analysis of nitrates, which measures the volume of NO liberated by
Stoichiometry II: Calculations Based on Chemical Equations
(a) What weight of copper and (b) how many moles of HNO 3 are needed to
prepare 500 ml NO, measured over water at 730 torr and 25°C?
(c) If the nitric acid solution contains 10.0 moles/liter, what volume of the
solution is used?
13. Arsenic compounds may be detected easily by the Marsh test. In this test,
some metallic zinc is added to an acid solution of the material to be tested, and
the mixture is heated. The arsenic is liberated as arsine, AsH 3 , which may be
decomposed by heat to give an "arsenic mirror." The reaction is
4Zn + H 3 AsO 4 + 8HC1 -^ 4ZnCl 2 + AsH 3 + 4H 2 O
What volume of AsH 3 at 720 torr and 25°C is evolved by 7.00 x 10~
7 g of
arsenic, the smallest amount of arsenic that can be detected with certainty by
this method?
14. H 2 S gas will cause immediate unconsciousness at a concentration of 1 part per
1000 by volume. What weight of FeS is needed to fill a room 20 ft x 15 ft x 9 ft
with H 2 S at this concentration? Barometric pressure is 740 torr, and the temperature is 80°F. The reaction is
FeS + 2HC1 -> FeCl 2 + H 2 S
15. The Mond process separates nickel from other metals by passing CO over the
hot metal mixture. The nickel reacts to form a volatile compound (called
nickel carbonyl), which is then swept away by the gas stream. The reaction is
Ni + 4CO -^ Ni(CO) 4
How many cubic feet of CO at 3.00 atm and 65°Fare needed to react with 1.00
ton of nickel?
16. A cement company produces 100 tons of cement per day. Its product contains
62.0% CaO, which is prepared by calcining limestone by the reaction
CaCO 3 -^ CaO + CO 2
What volume of CO 2 at 735 torr and 68°F is sent into the air around the plant
each day as a result of this calcination?
17. The Ostwald process of making HNO 3 involves the air oxidation of NH 3 over
a platinum catalyst. The first two steps in this process are
4NH 3 + 50 2 -^ 6H 2 O + 4NO
2ND + O 2 ^ 2NO 2
How many cubic feet of air (21% O 2 by volume) at 27°C and 1.00 atm are
needed for the conversion of 50.0 tons of NH 3 to NO 2 by this process?
18. How many cubic feet of air (21% O 2 by volume) are needed for the production
of 10
5 ft
3 NO 2 at the same conditions as those used to measure the air? (See
Problem 17 for the equations involved.)
19. The du Pont company has developed a nitrometer, an apparatus for the rapid
routine analysis of nitrates, which measures the volume of NO liberated by