Page 171 - Theory and Problems of BEGINNING CHEMISTRY

160 STOICHIOMETRY [CHAP. 10

10.64. (a) When 5.00 g NaOH reacts with 5.00 g HCl, how much NaCl is produced? (b) When 6.00 g NaOH reacts with
5.00 g HCl, how much NaCl is produced?
Ans. HCl + NaOH −→ NaCl + H 2 O

(a) 1 mol HCl
5.00 g HCl = 0.137 mol HCl
36.5 g HCl

1 mol NaOH
5.00 g NaOH = 0.125 mol NaOH
40.0 g NaOH
Since the reactants react in a 1:1 ratio, NaOH is the limiting quantity:

1 mol NaCl 58.5 g NaCl
0.125 mol NaOH = 7.31 g NaCl
1 mol NaOH 1 mol NaCl

(b) 1 mol NaOH
6.00 g NaOH = 0.150 mol NaOH
40.0 g NaOH
1 mol HCl

5.00 g HCl = 0.137 mol HCl
36.5 g HCl
Since the reactants react in a 1:1 ratio, HCl is the limiting quantity:
1 mol NaCl 58.5 g NaCl

0.137 mol HCl = 8.01 g NaCl
1 mol HCl 1 mol NaCl
10.65. Calculate the number of moles of each solute in the final solution after 1.75 mol of aqueous BaCl 2 and 2.70 mol of
aqueous AgNO 3 are mixed.
Ans. BaCl 2 + 2 AgNO 3 −→ Ba(NO 3 ) 2 + 2 AgCl(s)
Initial: 1.75 mol 2.70 mol 0.00 mol
Change: 1.35 mol 2.70 mol 1.35 mol
Final: 0.40 mol 0.00 mol 1.35 mol

10.66. Calculate the number of moles of each ion in the final solution after 1.75 mol of aqueous BaCl 2 and 2.70 mol of
aqueous AgNO 3 are mixed.

Ans. The Ba 2+ ion and the NO 3 ion do not react (they are spectator ions), so there are 1.75 mol of Ba 2+ ion
−
−
and 2.70 mol of NO 3 ion in the final solution. The silver ion and chloride ion concentrations are calculated
using the net ionic equation:
Cl − + Ag + −→ AgCl(s)
Initial: 3.50 mol 2.70 mol
Change: 2.70 mol 2.70 mol
Final: 0.80 mol 0.00 mol
These results are the same as those of the prior problem.

10.67. Consider the reaction
Ba(OH) 2 + 2 HCl −→ BaCl 2 + 2H 2 O
If exactly 20.0 g of Ba(OH) 2 reacts according to this equation, do you know how much Ba(OH) 2 was added to the
HCl? Do you know how much HCl was added to the Ba(OH) 2 ? Explain.
Ans. You cannot tell. Either reactant might have been in excess. The information given allows calculations of how
much reacted and how much of the products were produced, but not how much was added in the first place.

10.68. Redo Problem 10.18 without bothering to solve for intermediate answers.
10.69. Determine the number of grams of SO 3 produced by treating excess SO 2 with 50.0 g of oxygen.
Ans. 250 g.