Question

A gaseous alkane is exploded with oxygen .The moles of oxygen for complete combustion and carbon dioxide formed is in the ratio 7:4.Deduce the molecular formula of the alkane

Answer 1

General equation for combustion :CxHy + (x+y/4)O2 → xCO2 + y/2H2O​According to question :(x+(y/4))/x = 7/4Solving the equation we obtain:4x + y = 7x ory=3xy/x = 3/1Thus the alkane is of the type:CxH3xGaseous alkanes are CH4 , C2H6 , C3H8 ,C4H10 only and only gaseous alkane with formula of this type is C2H6.

Answer 2

Answer:C2H6

Explanation:CnH2n+2 +(n+(n+1)/2)O2-nCO2+(n+1)H2O

Vol. Of O2 used/Vol.of CO2 form=7/4

Vol.of O2 used=n+(n+1/2)

Vol.of CO2 formed =n

n+(n+1/2)/n=7/4

(3n+1/2)/n=7/4

(12n+4)/2=7n

6n+2=7n

2=7n-6n

2=n

C2H6