Chapter 7, Problem 5STP

Interpretation Introduction

Interpretation: The sum of the coefficients of the following reaction needs to be determined when the reaction is balanced:

  $\text{FeS(s) + HCl(g) }\to {\text{FeCl}}_{\text{2}}\text{(s})+{\text{H}}_{\text{2}}\text{S(g)}$

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

Answer to Problem 5STP

The correct option is (a): $\text{5}$ .

Explanation of Solution

The given reaction is:

  $\text{FeS(s) + HCl(g) }\to {\text{FeCl}}_{\text{2}}\text{(s})+{\text{H}}_{\text{2}}\text{S(g)}$

The reaction is not balanced as the number of H and Cl atoms in the reactant side is 1 and on the product side is 2. So, in order to balance the reaction, coefficient 2 is written before HCl on the reactant side. So, the balanced chemical reaction is:

  $\text{FeS(s) + 2HCl(g) }\to {\text{FeCl}}_{\text{2}}\text{(s})+{\text{H}}_{\text{2}}\text{S(g)}$

The coefficients for each compound involved in the reaction are:

  $\begin{array}{l}\text{FeS(s) = 1}\\ \text{HCl(g) = 2 }\\ {\text{FeCl}}_{\text{2}}\text{(s})=1\\ {\text{H}}_{\text{2}}\text{S(g) = 1}\end{array}$

Hence, the sum of the coefficients of the balanced reaction is:

  $\text{1 + 2 + 1 + 1 = 5}$