Page 163 - Theory and Problems of BEGINNING CHEMISTRY

152 STOICHIOMETRY [CHAP. 10

Avogadro’s Formula units
Moles NaOH
number NaOH

Balanced Balanced
chemical chemical
equation equation

Moles Avogadro’s Formula units
number
Na 2 SO 4 Na 2 SO 4
Fig. 10-4. Conversion of formula units of a reactant to formula units of a product

Ans. (a) KOH may be used: H 3 PO 4 + 2KOH −→ K 2 HPO 4 + 2H 2 O

1 mol H 3 PO 4
(b) 6.00 mol K 2 HPO 4 = 6.00 mol H 3 PO 4
1 mol K 2 HPO 4
2 mol KOH

(c) 6.00 mol K 2 HPO 4 = 12.0 mol KOH
1 mol K 2 HPO 4

56.1gKOH
(d) 12.0 mol KOH = 673 g KOH
1 mol KOH
10.19. Determine the number of grams of hydrochloric acid that will just react with 20.0 g of calcium carbonate
to produce carbon dioxide, water, and calcium chloride.
Ans. CaCO 3 + 2 HCl −→ CaCl 2 + H 2 O + CO 2

1 mol CaCO 3 2 mol HCl 36.5 g HCl
20.0 g CaCO 3 = 14.6 g HCl
100 g CaCO 3 1 mol CaCO 3 1 mol HCl
10.20. How many grams of Hg 2 Cl 2 can be prepared from 15.0 mL of mercury (density 13.6 g/mL)?
Ans. 2Hg + Cl 2 −→ Hg 2 Cl 2

13.6gHg 1 mol Hg 1 mol Hg 2 Cl 2 471gHg 2 Cl 2
15.0mLHg = 239gHg 2 Cl 2
1mLHg 200.6gHg 2 mol Hg 1 mol Hg 2 Cl 2
10.21. How many grams of methyl alcohol, CH 3 OH, can be obtained in an industrial process from 5.00 metric
6
tons (5.00 × 10 g) of CO plus hydrogen gas? To calculate the answer: (a) Write a balanced chemical
6
equation for the process. (b) Calculate the number of moles of CO in 5.00 × 10 g CO. (c) Calculate the
number of moles of CH 3 OH obtainable from that number of moles of CO. (d) Calculate the number of
grams of CH 3 OH obtainable.
special conditions
Ans. (a)CO + 2H 2 −−−−−−−→ CH 3 OH

1 mol CO
5
6
(b)5.00 × 10 gCO = 1.79 × 10 mol CO
28.0gCO

1 mol CH 3 OH
5
5
(c) 1.79 × 10 mol CO = 1.79 × 10 mol CH 3 OH
1 mol CO
32.0gCH 3 OH

6
5
(d)1.79 × 10 mol CH 3 OH = 5.73 × 10 gCH OH
3
1 mol CH 3 OH
10.22. Determine the number of grams of barium hydroxide it would take to neutralize (just react completely,
with none left over) 14.7 g of phosphoric acid.