Question

Characterize a system at chemical equilibrium with respect to each of the following:

a. the rates of the forward and reverse reactions

b. the overall composition of the reaction mixture

For a general reaction 3A(g) + B(g) → 2C (g), if one starts an experiment with only reactants present, show what the plot of concentrations of A, B, and C versus time would look like. Also, sketch the plot illustrating the rate of the forward reaction and rate of the reverse reaction versus time.

Answer 1

a) When a system is attained chemical; equilibrium rate of forward reaction will be equal to the rate of backward reaction.

b) The overall composition of the reaction mixture remains constant once the reaction is at equilibrium position.

At the starting of the reaction concentrations of reactants is more. So rate of the forward reaction is also high. But as the reaction proceeds reactants are consumed and products are formed. So rate of forward reaction decreases and back ward reaction increases. Finally a stage is attained where both the rates of the reaction are same. That can be plotted as follows.