Decomposition of H2O2 follows a first order reaction. In fifty minutes the concentration of H2O2 decreases from 0.5 to 0.125 M in one such decomposition. When the concentration of H2O2 reaches 0.05 M, the rate of formation of O2 will be:
Rate = k[H2O2]=0.69325×0.05
Rate of formation of H2O2=12×0.69325×0.05
=6.93×10−4mol min−1