Chapter 18, Problem 84A

Interpretation Introduction

Interpretation: The effect of the change in the concentration of the reactant on the reaction rate and equilibrium position is to be explained.

Concept introduction: The rate at which a chemical reaction occurs is referred to as its reaction rate. It is expressed as either the concentration of a reactant that is consumed or the concentration of a product that is generated in a unit of time.

Answer to Problem 84A

The higher the concentration of reactants, the greater the reaction rate. If the amount of a reactant increases, the equilibrium will shift toward the reaction that uses up the reactant.

Explanation of Solution

The reversible reaction is as follows:

  $2{\text{NO}}_{\text{2}}\left(g\right)\rightleftharpoons {\text{N}}_{\text{2}}{\text{O}}_4\left(g\right)$

When the concentration of ${\text{NO}}_{\text{2}}$ is changed from $0.020{\text{ mol L}}^{-1}$ to $0.030{\text{ mol L}}^{-1}$ , it will affect the rate of the given reaction and equilibrium position.

When the concentration of reactants is increased, more particles of reactants move together. Since there will be more collisions, the rate of reaction will increase. The rate of a reaction will increase in proportion to the concentration of the reactants. In other words, higher concentrations result in a higher reaction rate.

If the concentration of a substance is changed, the equilibrium will shift in order to minimize the effect. If the concentration of a reactant is increased, equilibrium will shift toward the reaction that consumes the reactants, causing the concentration of the reactant to decrease.

Conclusion

The higher the concentration of reactants, the greater the reaction rate. If the amount of a reactant increases, the equilibrium will shift toward the reaction that uses up the reactant.