Initially,concentrations of H2 and I2 are large,only the forward reaction occurs;As time passes,the concentrations of H,and I, decrease and in result the forward reaction slows down.The concentrations of HI increase and in result the reverse reaction speeds up. The reaction mixture is at equilibrium until the forward and reverse reactions go at the same rate. Initially, concentrations of H2 and I2 are large, only the forward reaction occurs; As time passes, the concentrations of H2 and I2 decrease and in result the forward reaction slows down. The concentrations of HI increase and in result the reverse reaction speeds up. The reaction mixture is at equilibrium until the forward and reverse reactions go at the same rate