Page 139 - Theory and Problems of BEGINNING CHEMISTRY

128 CHEMICAL EQUATIONS [CHAP. 8

Solved Problems

INTRODUCTION
8.1. How many oxygen atoms are there in each of the following, perhaps part of a balanced chemical equation?
(a)7H 2 O, (b)4Ba(NO 3 ) 2 ,(c) 2 CuSO 4 ·5H 2 O, and (d )4VO(ClO 3 ) 2 .
Ans. (a)7,(b) 24, (c) 18, and (d) 28.

BALANCING SIMPLE EQUATIONS
heat
8.2. Balance the following equation: C + Cu 2 O −→ CO + Cu
Ans. C + Cu 2 O −→ CO + 2Cu

8.3. Balance the following equation:
Ca(HCO 3 ) 2 + H 3 PO 4 −→ Ca 3 (PO 4 ) 2 + H 2 O + CO 2
Ans. ?Ca(HCO 3 ) 2 + ?H 3 PO 4 −→ 1Ca 3 (PO 4 ) 2 + ?H 2 O + ?CO 2
3Ca(HCO 3 ) 2 + 2H 3 PO 4 −→ 1Ca 3 (PO 4 ) 2 + 6H 2 O + 6CO 2
2nd 2nd 3rd 3rd
3Ca(HCO 3 ) 2 + 2H 3 PO 4 −→ Ca 3 (PO 4 ) 2 + 6H 2 O + 6CO 2
8.4. Balance the following equation:
NH 4 Cl + KOH −→ NH 3 + H 2 O + KCl

Ans. 1NH 4 Cl + ?KOH −→ ?NH 3 + ?H 2 O + ? KCl
Balance N and Cl : 1 NH 4 Cl + ?KOH −→ 1NH 3 + ?H 2 O + 1 KCl
Balance K : 1 NH 4 Cl + 1KOH −→ 1NH 3 + ?H 2 O + 1 KCl
Balance H : 1 NH 4 Cl + 1KOH −→ 1NH 3 + 1H 2 O + 1 KCl
Eliminate 1s : NH 4 Cl + KOH −→ NH 3 + H 2 O + KCl
8.5. Balance the following equation

NH 4 Cl + NaOH + AgCl −→ Ag(NH 3 ) 2 Cl + NaCl + H 2 O
Ans. ?NH 4 Cl + ? NaOH + ? AgCl −→ 1Ag(NH 3 ) 2 Cl + ? NaCl + ?H 2 O
2NH 4 Cl + 2 NaOH + 1 AgCl −→ 1Ag(NH 3 ) 2 Cl + 2 NaCl + 2H 2 O
2nd 4th 2nd 3rd 5th
2NH 4 Cl + 2 NaOH + AgCl −→ Ag(NH 3 ) 2 Cl + 2 NaCl + 2H 2 O

8.6. Balance the following chemical equations:

(a) NCl 3 + H 2 O −→ HClO + NH 3
(b) NaOH + H 3 PO 4 −→ Na 2 HPO 4 + H 2 O

(c)Al + HCl −→ AlCl 3 + H 2
(d) HCl + Mg −→ MgCl + H 2
2
(e) SrCO 3 + HClO 4 −→ Sr(ClO 4 ) 2 + CO 2 + H 2 O
(f) KC 2 H 3 O 2 + HBr −→ KBr + HC 2 H 3 O 2
(g)Ba(OH) 2 + H 3 PO 4 −→ BaHPO 4 + H 2 O
(h) HCl + Na 3 PO 4 −→ NaCl + NaH 2 PO 4
Ans. (a) NCl 3 + 3H 2 O −→ 3 HClO + NH 3
(b) 2 NaOH + H 3 PO 4 −→ Na 2 HPO 4 + 2H 2 O