204
Stolchlometry III: Calculations Based on Concentrations of Solutions
50.00 ml of 1.2000 M HC1; 3.65 ml of 0.5316 M NaOH is required for backtitration. Calculate the percentage of NH 3 in the sample.
47. A 0.5000 g sample of impure CaO is added to 50.00 ml of 0.1000 M HC1. The
excess HC1 is titrated by 5.00 ml of 0.1250 M NaOH. Find the percentage of
CaO in the sample. The reaction is
CaO + 2HC1 -+ CaCl 2 + H 2 O
48. Silver nitrate solution is prepared by dissolving 85.20 g of pure AgNO 3 and
diluting to 500.0 ml.
(a) What is its molarity?
(b) A CaCl 2 sample is titrated by 40.00 ml of this AgNO 3 solution. What is the
weight of CaCl 2 in the sample?
49. (a) What weight of MnO 2 and (b) what volume of 12.0 M HC1 are needed for
the preparation of 750 ml of 2.00 M MnCl 2 ? (c) What volume of C1 2 at 745 torr
and 23°C will be formed? The reaction is
MnO 2 + 4HC1 -* MnCl 2 + C1 2 + 2H 2 O
50. What volume of 12.0 M HC1 is needed to prepare 3.00 liters of C1 2 at 730 torr
and 25°C by the reaction
2KMn0 4 + 16HC1 -* 2MnCl 2 + 5C1 2 + 8H 2 O + 2KC1
51. (a) What volume of 6.00 M HNO 3 and what weight of copper are needed for
the production of 1.50 liters of a 0.500 M Cu(NO 3 ) 2 solution?
(b) What volume of NO, collected over water at 745 torr and 18°C, will be
produced at the same time? The reaction is
3Cu + 8HNO 3 -* 3Cu(NO 3 ) 2 + 2NO + 4H 2 O
52. What volume of 10.0 M HC1 is needed to prepare 12.7 liters of CO 2 at 735 torr
and 35°C? The reaction is
CaCO 3 + 2HC1 -» CaCl 2 + CO 2 + H 2 O
53. A 20.00 ml sample of a solution containing NaNO 2 and NaNO 3 is acidified
with H 2 SO 4 and then treated with an excess of NaN 3 (sodium azide). The
hydrazoic acid so formed reacts with and completely removes the HNO 2 . It
does not react with the nitrate. The reaction is
HN 3 + HNO 2 -> H 2 O + N 2 + N 2 O
The volume of N 2 and N 2 O is measured over water and found to be 36.50 ml at
740.0 torr and 27°C. What is the molar concentration of NaNO 2 in this solution?
54. You have a 0.5000 g mixture of oxalic acid, H 2 C 2 O 4 -2H 2 O, and benzoic acid,
HC 7 H 5 O 2 . This sample requires 47.53 ml of 0.1151 M KOH for titration. What
is the percentage composition of this mixture?
Stolchlometry III: Calculations Based on Concentrations of Solutions
50.00 ml of 1.2000 M HC1; 3.65 ml of 0.5316 M NaOH is required for backtitration. Calculate the percentage of NH 3 in the sample.
47. A 0.5000 g sample of impure CaO is added to 50.00 ml of 0.1000 M HC1. The
excess HC1 is titrated by 5.00 ml of 0.1250 M NaOH. Find the percentage of
CaO in the sample. The reaction is
CaO + 2HC1 -+ CaCl 2 + H 2 O
48. Silver nitrate solution is prepared by dissolving 85.20 g of pure AgNO 3 and
diluting to 500.0 ml.
(a) What is its molarity?
(b) A CaCl 2 sample is titrated by 40.00 ml of this AgNO 3 solution. What is the
weight of CaCl 2 in the sample?
49. (a) What weight of MnO 2 and (b) what volume of 12.0 M HC1 are needed for
the preparation of 750 ml of 2.00 M MnCl 2 ? (c) What volume of C1 2 at 745 torr
and 23°C will be formed? The reaction is
MnO 2 + 4HC1 -* MnCl 2 + C1 2 + 2H 2 O
50. What volume of 12.0 M HC1 is needed to prepare 3.00 liters of C1 2 at 730 torr
and 25°C by the reaction
2KMn0 4 + 16HC1 -* 2MnCl 2 + 5C1 2 + 8H 2 O + 2KC1
51. (a) What volume of 6.00 M HNO 3 and what weight of copper are needed for
the production of 1.50 liters of a 0.500 M Cu(NO 3 ) 2 solution?
(b) What volume of NO, collected over water at 745 torr and 18°C, will be
produced at the same time? The reaction is
3Cu + 8HNO 3 -* 3Cu(NO 3 ) 2 + 2NO + 4H 2 O
52. What volume of 10.0 M HC1 is needed to prepare 12.7 liters of CO 2 at 735 torr
and 35°C? The reaction is
CaCO 3 + 2HC1 -» CaCl 2 + CO 2 + H 2 O
53. A 20.00 ml sample of a solution containing NaNO 2 and NaNO 3 is acidified
with H 2 SO 4 and then treated with an excess of NaN 3 (sodium azide). The
hydrazoic acid so formed reacts with and completely removes the HNO 2 . It
does not react with the nitrate. The reaction is
HN 3 + HNO 2 -> H 2 O + N 2 + N 2 O
The volume of N 2 and N 2 O is measured over water and found to be 36.50 ml at
740.0 torr and 27°C. What is the molar concentration of NaNO 2 in this solution?
54. You have a 0.5000 g mixture of oxalic acid, H 2 C 2 O 4 -2H 2 O, and benzoic acid,
HC 7 H 5 O 2 . This sample requires 47.53 ml of 0.1151 M KOH for titration. What
is the percentage composition of this mixture?