Correct option is (a) 9.3 minutes
As we know,
Rate of diffusion \(\propto \sqrt{\frac 1M}\)
\(\therefore \frac{\frac 1{t_{O_2}}}{\frac1{t_{N_2}}} = \sqrt{\frac{M_{N_2}}{M_{O_2}}} = \sqrt {\frac{2.8}{3.2}} = 0.93\)
or \(\frac{t_{N_2}}{t_{O_2}} = 0.93\)
\(\therefore t_{N_2} = 0.93 \times 10 = 9.3 \ min\)
