Chapter U4, Problem 4RE

(a)

Interpretation Introduction

Interpretation:

The balanced chemical equation for the given chemical reaction of calcium and water needs to be determined.

Concept Introduction:

The chemical reaction must be balanced such that it agrees with the law of mass conservation. A balanced chemical equation arises when the number of atoms or ions of reactant side are equals to the number of atom or ions of product side.

Answer to Problem 4RE

The balance chemical equation is:

  ${\text{Ca}}_{\text{(s)}}{\text{ + 2H}}_{\text{2}}{\text{O}}_{\text{(l)}}\to {\text{ Ca(OH)}}_{\text{2}}{}_{\text{(aq) }}{\text{ + H}}_2{}_{(g)}$

Explanation of Solution

When the reaction of calcium metal (Ca) react with water (H₂O) to gives the calcium hydroxide (Ca(HO)₂) in aqueous solution and hydrogen (H₂) gas.

The unbalance reaction is

  ${\text{Ca}}_{\text{(s)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\to {\text{ Ca(OH)}}_{\text{2}}{}_{\text{(aq) }}{\text{ + H}}_2{}_{(g)}$

The above reaction can be balanced by giving coefficient 2 to H₂O.

Thus, the balanced chemical equation will be:

  ${\text{Ca}}_{\text{(s)}}{\text{ + 2H}}_{\text{2}}{\text{O}}_{\text{(l)}}\to {\text{ Ca(OH)}}_{\text{2}}{}_{\text{(aq) }}{\text{ + H}}_2{}_{(g)}$

(b)

Interpretation Introduction

Interpretation:

The balanced chemical equation for the given chemical reaction of calcium bicarbonate and hydrochloric acid needs to be determined.

Concept Introduction:

The chemical reaction must be balanced such that it agrees with the law of mass conservation. A balanced chemical equation arises when the number of atoms or ions of reactant side are equals to the number of atom or ions of product side.

Answer to Problem 4RE

  ${\text{2HCl}}_{\text{(aq)}}{\text{ + Ca(HCO}}_{\text{3}}{\text{)}}_{\text{2(s)}}\to {\text{ 2H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + 2CO}}_{\text{2(g)}}{\text{ + CaCl}}_{\text{2(s)}}$

Explanation of Solution

The reaction of calcium bicarbonate ${\text{Ca(HCO}}_{\text{3}}{\text{)}}_{\text{2(s)}}$ with aqueous hydrochloric acid gives carbon dioxide gas, water and calcium chloride ${\text{CaCl}}_{\text{2(s)}}$ in solid form.

The unbalanced reaction is:

  ${\text{HCl}}_{\text{(aq) }}{\text{+ Ca(HCO}}_{\text{3}}{\text{)}}_{\text{2(s)}}\to {\text{ H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + CO}}_{\text{2(g)}}{\text{ + CaCl}}_{\text{2(s)}}$

The above reaction can be balanced by giving coefficient 2 to HCl, 2 to H₂O and 2 to CO₂.

Thus, the balanced chemical reaction will be:

  ${\text{2HCl}}_{\text{(aq)}}{\text{ + Ca(HCO}}_{\text{3}}{\text{)}}_{\text{2(s)}}\to {\text{ 2H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + 2CO}}_{\text{2(g)}}{\text{ + CaCl}}_{\text{2(s)}}$