Question

balancing equations worksheet

1. for each of the following write the correct skeleton equation, then balance it to form

a chemical equation and state the type of reaction.
a) copper (ii) oxide + hydrogen → copper + water
skeleton equation
chemical equation
type of reaction
b) lead (ii) nitrate + potassium iodide → lead (ii) iodide + potassium nitrate
skeleton equation
chemical equation
type of reaction
c) calcium + water → calcium hydroxide + hydrogen gas
skeleton equation
chemical equation
type of reaction
d) lead (ii) sulfide + oxygen → lead + sulfur dioxide
skeleton equation
chemical equation
type of reaction
e) hydrogen sulfide → hydrogen + sulfur
skeleton equation
chemical equation
type of reaction
f) gasoline + oxygen → carbon dioxide + water + energy
skeleton equation
chemical equation
type of reaction
(the chemical formula for gasoline is c₇h₁₆)

Explanation:

Step1: Write skeleton equations

Use chemical formulas. For example, copper (II) oxide is \(CuO\), hydrogen is \(H_2\), copper is \(Cu\), water is \(H_2O\). So for part a), the skeleton equation is \(CuO + H_2
ightarrow Cu + H_2O\).

Step2: Balance chemical equations

Use the law of conservation of mass. For \(CuO + H_2
ightarrow Cu + H_2O\), the atoms of each element on both sides are already equal. So the balanced chemical equation is \(CuO + H_2 = Cu + H_2O\).

Step3: Determine reaction types

• a) In \(CuO + H_2 = Cu + H_2O\), hydrogen displaces copper from copper (II) oxide. So it is a single - displacement reaction.
• b) Skeleton equation: \(Pb(NO_3)_2+KI

ightarrow PbI_2 + KNO_3\). Balance: \(Pb(NO_3)_2 + 2KI=PbI_2+2KNO_3\). Type: Double - displacement reaction (exchange of ions).

• c) Skeleton: \(Ca + H_2O

ightarrow Ca(OH)_2+H_2\). Balance: \(Ca + 2H_2O=Ca(OH)_2 + H_2\). Type: Single - displacement reaction (calcium displaces hydrogen).

• d) Skeleton: \(PbS+O_2

ightarrow Pb+SO_2\). Balance: \(2PbS + 3O_2=2Pb+2SO_2\). Type: Oxidation - reduction (redox) reaction (sulfur is oxidized, oxygen is reduced).

• e) Skeleton: \(H_2S

ightarrow H_2+S\). Balance: \(H_2S = H_2+S\). Type: Decomposition reaction (one compound breaks into two).

• f) Skeleton: \(C_7H_{16}+O_2

ightarrow CO_2 + H_2O\). Balance: \(C_7H_{16}+11O_2 = 7CO_2+8H_2O\). Type: Combustion reaction (hydrocarbon reacts with oxygen to produce \(CO_2\) and \(H_2O\)).

Answer:

a)

• Skeleton equation: \(CuO + H_2

ightarrow Cu + H_2O\)

• Chemical equation: \(CuO + H_2 = Cu + H_2O\)
• Type of reaction: Single - displacement reaction

b)

• Skeleton equation: \(Pb(NO_3)_2+KI

ightarrow PbI_2 + KNO_3\)

• Chemical equation: \(Pb(NO_3)_2 + 2KI=PbI_2+2KNO_3\)
• Type of reaction: Double - displacement reaction

c)

• Skeleton equation: \(Ca + H_2O

ightarrow Ca(OH)_2+H_2\)

• Chemical equation: \(Ca + 2H_2O=Ca(OH)_2 + H_2\)
• Type of reaction: Single - displacement reaction

d)

• Skeleton equation: \(PbS+O_2

ightarrow Pb+SO_2\)

• Chemical equation: \(2PbS + 3O_2=2Pb+2SO_2\)
• Type of reaction: Oxidation - reduction (redox) reaction

e)

• Skeleton equation: \(H_2S

ightarrow H_2+S\)

• Chemical equation: \(H_2S = H_2+S\)
• Type of reaction: Decomposition reaction

f)

• Skeleton equation: \(C_7H_{16}+O_2

ightarrow CO_2 + H_2O\)

• Chemical equation: \(C_7H_{16}+11O_2 = 7CO_2+8H_2O\)
• Type of reaction: Combustion reaction