Chapter 17, Problem 28A

Interpretation Introduction

Interpretation: The effect of addition of reactant in the reaction equilibrium needs to be explained.

Concept introduction: According to Le Chatelier's principle if any stress is given to the equilibrium, it will shift in a direction to reduce the given stress. If change in concentration, pressure or temperature takes place at equilibrium, it will shift in the direction to undo the change or its effect.

Answer to Problem 28A

Amount the product increases when reactant is added. The value of equilibrium constant does not change.

Explanation of Solution

Consider a hypothetical reaction: $A+2B\rightleftharpoons C+D$

Equilibrium constant for the reaction is given by the equation, $K=\frac{\left[C\right]\left[D\right]}{\left[A\right]{\left[B\right]}^2}$

If we add a reactant (say $A$ ) then the value of $K$ will decrease because the concentration of $A$ is in denominator. To maintain the value of $K$ , concentration of the products ( $C$ and $D$ ) must increase. Hence, even upon addition of reactant the value $K$ will not change.

Conclusion

Amount the product increases when reactant is added. The value of equilibrium constant does not change.