Chapter 17, Problem 13A

Interpretation Introduction

Interpretation: Whether a reaction is in chemical equilibrium or not needs to be explained. This is to be explained how the chemical equilibrium is denoted while writing a reaction.

Concept introduction: Reaction quotient $Q$ is a quantity that used to determine in which direction the reaction will shift to approach equilibrium.

Consider a reaction: $A\left(g\right)\rightleftharpoons B\left(g\right)$

The expression for $Q$$=\frac{[B]}{[A]}$

So, the reaction quotient  $Q$  is a ratio amounts of products and reactants present in a reaction at a given time not just equilibrium.

Whereas equilibrium constant $K$ is similar to that of $Q$ but used when equilibrium is achieved.

Answer to Problem 13A

When $Q=K$ then chemists can recognize equilibrium is achieved.

Equilibrium is denoted by the sign “ $\rightleftharpoons$ ”.

Explanation of Solution

When $Q=K$ concentration of the products is equal to the concentration of the reactants. It means both forward and backward reaction is occurring at same rate and hence it appears that the concentration of the products and reactants are not changing.

Conclusion

When $Q=K$ then chemists can recognize equilibrium is achieved.

Equilibrium is denoted by the sign “ $\rightleftharpoons$ ”.