Rate of formation of SO3 in the following reaction 2SO2+O2→2SO3 is 100 g min−1. Hence, rate of disappearance of O2 is:
For the reaction:2SO2+O2→2SO3
The rate in terms of reactants is given as negative as the concentration of reactants is decreasing with time whereas the rate in terms of products is given as positive as the concentration of products is increasing with time.
Rate=−1d[SO2]2dt=−d[O2]dt=+1d[SO3]2dt
Given. +1d[SO3]dt=100 g/min
−d[O2]dt=+1d[SO3]2dt
−d[O2]dt=12×100 g/min
−d[O2]dt=50 g/min
Thus, option A is correct.