A mixture of a mol of `C_(3) H_(8)` and `b` mol of `C_(2) H_(4)` was kept is a container of `V L` exerts a pressure of 4.93 atm at temperature `T`. Mixture was burnt in presence of `O_(2)` to convert `C_(3) H_(8)` and `C_(2) H_(4)` into `CO_(2)` in the container at the same temperature. The pressure of gases after the reaction and attaining the thermal equilirium with atomsphere at temperature `T` was found to be 11.08 atm.
The moles of `O_(2)` needed for combustion at temperature `T` is equal to

Options

A. `14 a`
B. `14 b`
C. `15 a`
D. `12 b`

Answer

A

Explanation

moles of `C_(5) H_(8) +` moles of `C_(2) H_(4) = a + b`
`= a + 3a = 4a`
Mole of `O_(2) = 5a + 3b = 5a + 3 xx 3a = 14 a`