A vessel contains equal volumes of SO2 and CH4. Through a small hole, the gases effused into vacuum. After 200sec, the total volume is reduced to half. What is the ratio of SO2 and CH4 remaining in the vessel?

Ratio of rates of diffusions of SO2 & CH4 =  1:2Moles ratio diffused  = 1:2Moles diffused   ∝ Volume diffusedLet total volume diffused =  2 + 1 = 3Volume of CH4 not diffused = 3 - 1 = 2 Volume of SO2 not diffused = 3 - 2 = 1Required ratio   = 2 : 1