Chapter 17, Problem 23A

Interpretation Introduction

Interpretation: Homogeneous equilibrium system and heterogeneous equilibrium system has to be explained with examples and chemical equations.

Concept Introduction: The term “Equilibrium” stands for balance (or) steadiness. In other words, chemical equilibrium can be defined as the balancing two chemical/physical processes in exact way; the one of the process is the opposite of other. A reaction is said to be chemical equilibrium, when the rates of the reactants and products are same.

When all the chemical species are in same phase, the equilibrium is called as homogeneous equilibrium.

When all the chemical species are in different phases, the equilibrium is called as heterogeneous equilibrium.

Answer to Problem 23A

In homogeneous equilibrium, the reactants and products are in the same phase. An example of homogeneous equilibrium is the combination reaction of nitrogen and oxygen to form nitrogen monoxide.

  $N_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2NO\left(g\right)$

In heterogeneous equilibrium, the reactants and the products are in different phase. Two examples of heterogeneous equilibrium are,

  $\begin{array}{l}CaC{O}_3\left(s\right)\rightleftharpoons CaO\left(s\right)+C{O}_2\left(g\right)\\ Br\left(l\right)\rightleftharpoons B{r}_2\left(g\right)\end{array}$

Explanation of Solution

For a balanced chemical reaction,

  $aA+bB\rightleftharpoons cC+dD$

Where,

• $A,B,C,D$ are chemical species.
• $a,b,c$ and $d$ are coefficients in the balanced equation.

The equilibrium expression is ratio of the concentration of the products to the concentration of the reaction. The concentration of each reactant/product is raised to a power corresponding to their coefficient in the balanced equation.

The equilibrium expression is given as,

  $K=\frac{{\left[C\right]}^c{\left[D\right]}^d}{{\left[A\right]}^a{\left[B\right]}^b}$

Where,

  $K$ is the value of equilibrium constant.

In homogeneous equilibrium, the reactants and products are in the same phase. Some examples of homogeneous equilibrium are,

• Reaction of nitrogen monoxide (in gas state) with oxygen (in gas state) forms nitrogen dioxide (in gas state).
• Gaseous hydrogen reacts with gaseous oxygen to form gaseous water.

An example of homogeneous equilibrium is reaction of nitrogen and oxygen to form nitrogen monoxide.

  $N_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2NO\left(g\right)$

In heterogeneous equilibrium, the reactants and the products are in different phase. Some examples of heterogeneous equilibria are,

• Thermal decomposition of calcium carbonate (in solid state) gives calcium oxide (in solid phase) and carbon dioxide (in gas state).
• Ammonium carbonate (in solid state) gives dinitrogen oxide (in gas state) and water (in gas state).
• Reaction of sulphur trioxide (in gas state) with water (in liquid state) gives sulfuric acid (in liquid state).

Two chemical equation as examples of heterogeneous equilibrium are,

  $\begin{array}{l}CaC{O}_3\left(s\right)\rightleftharpoons CaO\left(s\right)+C{O}_2\left(g\right)\\ Br\left(l\right)\rightleftharpoons B{r}_2\left(g\right)\end{array}$