Chapter 8, Problem 12A

Interpretation Introduction

Interpretation: The following precipitation reaction should be balanced:

  ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{(aq) + CaCl}}_{\text{2}}\text{(aq) }\to {\text{ CaSO}}_{\text{4}}\text{(s) + NaCl(aq)}$

Concept Introduction: The reactions for those the number of atoms of each element in the reactant and in the product, side are equal, such reactions are said to be a balanced chemical equation.

Answer to Problem 12A

  ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{(aq) + CaCl}}_{\text{2}}\text{(aq) }\to {\text{ CaSO}}_{\text{4}}\text{(s) + 2NaCl(aq)}$

Explanation of Solution

The given precipitation reaction is:

  ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{(aq) + CaCl}}_{\text{2}}\text{(aq) }\to {\text{ CaSO}}_{\text{4}}\text{(s) + NaCl(aq)}$

The given reaction is not balanced as the number of atoms of Na and Cl on the reactant is 2 whereas on the product side is 1 for each, so, in order to balance the reaction, coefficient 2 is written before NaCl on the product side. Thus, the balanced reaction is:

  ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{(aq) + CaCl}}_{\text{2}}\text{(aq) }\to {\text{ CaSO}}_{\text{4}}\text{(s) + 2NaCl(aq)}$

Interpretation Introduction

Interpretation: The following precipitation reaction should be balanced:

  $\text{Co}{\left({\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\right)}_{\text{2}}{\text{(aq) + Na}}_{\text{2}}\text{S(aq) }\to {\text{ CoS(s) + NaC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\text{(aq)}$

Concept Introduction: The reactions for those the number of atoms of each element in the reactant and in the product, side are equal, such reactions are said to be a balanced chemical equation.

Answer to Problem 12A

  $\text{Co}{\left({\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\right)}_{\text{2}}{\text{(aq) + Na}}_{\text{2}}\text{S(aq) }\to {\text{ CoS(s) + 2NaC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\text{(aq)}$

Explanation of Solution

The given precipitation reaction is:

  $\text{Co}{\left({\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\right)}_{\text{2}}{\text{(aq) + Na}}_{\text{2}}\text{S(aq) }\to {\text{ CoS(s) + NaC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\text{(aq)}$

The given reaction is not balanced as the number of atoms on reactant side is:

  $\begin{array}{l}\text{Na = 2}\\ \text{C = 4}\\ \text{H = 6}\\ \text{O = 4}\end{array}$

And on product side is:

  $\begin{array}{l}\text{Na = 1}\\ \text{C = 2}\\ \text{H = 3}\\ \text{O = 2}\end{array}$

So, in order to balance the reaction, coefficient 2 is written before ${\text{NaC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$ on the product side. Thus, the balanced reaction is:

  $\text{Co}{\left({\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\right)}_{\text{2}}{\text{(aq) + Na}}_{\text{2}}\text{S(aq) }\to {\text{ CoS(s) + 2NaC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}\text{(aq)}$

Interpretation Introduction

Interpretation: The following precipitation reaction should be balanced:

  ${\text{KOH(aq) + NiCl}}_{\text{2}}\text{(aq) }\to {\text{ Ni(OH)}}_2\text{(s) + KCl(aq)}$

Concept Introduction: The reactions for those the number of atoms of each element in the reactant and in the product, side are equal, such reactions are said to be a balanced chemical equation.

Answer to Problem 12A

  ${\text{2KOH(aq) + NiCl}}_{\text{2}}\text{(aq) }\to {\text{ Ni(OH)}}_2\text{(s) + 2KCl(aq)}$

Explanation of Solution

The given precipitation reaction is:

  ${\text{KOH(aq) + NiCl}}_{\text{2}}\text{(aq) }\to {\text{ Ni(OH)}}_2\text{(s) + KCl(aq)}$

The given reaction is not balanced as the number of atoms on reactant side is:

  $\begin{array}{l}\text{Cl = 2}\\ \text{H = 1}\\ \text{O = 1}\end{array}$

And on product side is:

  $\begin{array}{l}\text{Cl = 1}\\ \text{H = 2}\\ \text{O = 2}\end{array}$

So, in order to balance the reaction, coefficient 2 is written before KOH on the reactant side and coefficient 2 is written before KCl on the product side. Thus, the balanced reaction is:

  ${\text{2KOH(aq) + NiCl}}_{\text{2}}\text{(aq) }\to {\text{ Ni(OH)}}_2\text{(s) + 2KCl(aq)}$