Rate of formation of SO_{3} in the following reaction 2SO_{2} + O_{2} → 2SO_{3} is 100 g min^{–1}. Hence rate of disappearance of O_{2} is :
(A) 50 gmin^{-1}
(B) 40 gmin^{–1}
(C) 200 gmin^{–1}
(D) 20 gmin^{–1}
The correct answer is D) 20 g/min
Solution :: \({d\over dt} [SO_3]=100 g/min\)
\(={100\over80}mole/min =1.25 mole/min\)
\({-1\over2}{d\over dt}[SO_2]\)
\([SO_3]={-d\over dt}[O_2]={1\over2}{d\over dt}\)
\(={1.25\over2}\times 32mole/min \)
=20 g/min