Aktivity 3.17:
Balancing chemical equations
1. Write a balanced chemical equation for each of the following reactions:
(a) Nitrogen gas + Hydrogen gas → Ammonia gas
(b) Sodium metal + Water → Aqueous solution of sodium hydroxide + Hydrogen gas
(c) Solid copper(II) carbonate decomposes into solid copper(II) oxide and carbon dioxide gas when heated.
(d) Burning of aluminium powder in excess oxygen produces white aluminium oxide powder.
2. Balance the following chemical equations:
(a) KI(aq) + Br2(aq) → I2(s) + KBr(aq)
(b) Zn(s) + AgNO3(aq) → Zn(NO3)2(aq) + Ag(s)
(c) C3H8(g) + O2(g) → CO2(g) + H2O(l)
$$ \text { (d) } \mathrm{AgNO}_3(\mathrm{s}) \underset{\Delta}{\rightarrow} \mathrm{Ag}(\mathrm{s})+\mathrm{NO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) $$
Answer:
1. (a) $$ \mathrm{N}_2(\mathrm{~g})+3 \mathrm{H}_2(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_3(\mathrm{~g}) $$
(b) $$ 2 \mathrm{Na}(\mathrm{s})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{H}_2(\mathrm{~g}) $$
(c) $$ \mathrm{CuCO}_3(\mathrm{s}) \underset{\Delta}{\longrightarrow} \mathrm{CuO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g}) $$
(d) $$ 4 \mathrm{Al}(\mathrm{p})+3 \mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{Al}_2 \mathrm{O}_3(\mathrm{s}) $$
2. (a)$$ 2 \mathrm{KI}(\mathrm{aq})+\mathrm{Br}_2(\mathrm{aq}) \rightarrow \mathrm{I}_2(\mathrm{s})+2 \mathrm{KBr}(\mathrm{aq}) $$
(b) $$ \mathrm{Zn}(\mathrm{s})+2 \mathrm{AgNO}_3(\mathrm{aq}) \rightarrow \mathrm{Zn}\left(\mathrm{NO}_3\right)_2(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s}) $$
(c) $$ \mathrm{C}_3 \mathrm{H}_8(\mathrm{~g})+5 \mathrm{O}_2(\mathrm{~g}) \rightarrow 3 \mathrm{CO}_2(\mathrm{~g})+4 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) $$
(d) $$ 2 \mathrm{AgNO}_3(\mathrm{s}) \underset{\Delta}{\longrightarrow} 2 \mathrm{Ag}(\mathrm{s})+2 \mathrm{NO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) $$
Balancing chemical equations
1. Write a balanced chemical equation for each of the following reactions:
(a) Nitrogen gas + Hydrogen gas → Ammonia gas
(b) Sodium metal + Water → Aqueous solution of sodium hydroxide + Hydrogen gas
(c) Solid copper(II) carbonate decomposes into solid copper(II) oxide and carbon dioxide gas when heated.
(d) Burning of aluminium powder in excess oxygen produces white aluminium oxide powder.
2. Balance the following chemical equations:
(a) KI(aq) + Br2(aq) → I2(s) + KBr(aq)
(b) Zn(s) + AgNO3(aq) → Zn(NO3)2(aq) + Ag(s)
(c) C3H8(g) + O2(g) → CO2(g) + H2O(l)
$$ \text { (d) } \mathrm{AgNO}_3(\mathrm{s}) \underset{\Delta}{\rightarrow} \mathrm{Ag}(\mathrm{s})+\mathrm{NO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) $$
Answer:
1. (a) $$ \mathrm{N}_2(\mathrm{~g})+3 \mathrm{H}_2(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_3(\mathrm{~g}) $$
(b) $$ 2 \mathrm{Na}(\mathrm{s})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{H}_2(\mathrm{~g}) $$
(c) $$ \mathrm{CuCO}_3(\mathrm{s}) \underset{\Delta}{\longrightarrow} \mathrm{CuO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g}) $$
(d) $$ 4 \mathrm{Al}(\mathrm{p})+3 \mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{Al}_2 \mathrm{O}_3(\mathrm{s}) $$
2. (a)$$ 2 \mathrm{KI}(\mathrm{aq})+\mathrm{Br}_2(\mathrm{aq}) \rightarrow \mathrm{I}_2(\mathrm{s})+2 \mathrm{KBr}(\mathrm{aq}) $$
(b) $$ \mathrm{Zn}(\mathrm{s})+2 \mathrm{AgNO}_3(\mathrm{aq}) \rightarrow \mathrm{Zn}\left(\mathrm{NO}_3\right)_2(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s}) $$
(c) $$ \mathrm{C}_3 \mathrm{H}_8(\mathrm{~g})+5 \mathrm{O}_2(\mathrm{~g}) \rightarrow 3 \mathrm{CO}_2(\mathrm{~g})+4 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) $$
(d) $$ 2 \mathrm{AgNO}_3(\mathrm{s}) \underset{\Delta}{\longrightarrow} 2 \mathrm{Ag}(\mathrm{s})+2 \mathrm{NO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) $$