20 " mL of " a gasous bydrocarbon (A) was exploded with excess of `O_2` in an eudiometer tube. On cooling, the volume was reduced by 50 mL. On further treatment with KOH, there was further contraction of 40 mL. The molecular formula of the hydrocarbon A is
(a). `C_2H_6`
(b). `C_2H_4`
` C_3H_6`
(d). `C_3H_8`

Explanation

`C_(x)H_(y)(g)+(x+(y)/(4))O_2(g)toxCO_2(g)+(y)/(2)H_2O(l)`
`CO_2` is absorbed in KOH.
`therefore20x=40impliesx=2`
`20mL+20(2+(y)/(4))=40+50`
`20+40+(20y)/(4)=90`
`5y=90-60=30`
`y=6`
Formula of the compound is `C_2H_6`.