A gaseous mixture containing  CO,CH4 and N2 gas has total volume of 40ml. This mixture is exploded with excess of oxygen. On cooling the mixture, a contraction of 30ml is observed and when this mixture is exposed to aqueous KOH solution, a further contraction of 30ml is observed.  Then the composition of the mixture is ___?

Let volume of CO is “x” ml   volume of CH4is “y” mlVolume of  N2 is “z” mlCO(g)+1/2O2(g)→CO2(g)x ml                                   x mlCH4(g)+O2(g)→CO2(g)+2H2O(g)y ml                            y ml         2y” mlN2 remains unreactedOn cooling H2O(g) liquefied. So volume of reduction is 30ml.2y =  30 ;       y    =    15But volume of CO2obtained  =   (x+y) mlThis is absorbed in KOH & Volume  reduction of 30ml is observed.x+y    =   30(x    =   30 – y   =    30 – 15)  =    15and  x+y+z    =    40∴z=40-x-y=40-15-15=10Composition of mixture  isVol. of  CO    =     15 ml Vol. of CH4=15ml