In what ratio by mass, sulphur trioxide and nitrogen should be mixed so that the partial pressure exerted by each gas is same ?

Options

A. `7:20`
B. 7 `:` 40
C. 20 `:` 7
D. 40 `:` 7

Answer

C

Explanation

Partial pressure of a gas = Mole fraction Total pressure
For partial pressure to be equal,
`x ( SO_(3)) = x ( N_(2))`
`x ( SO_(3)) = ( W_(1) // 80)/( W_(1) // 80 + W_(2) // 28)`
and `x(N_(2)) = ( W_(2) // 28) / ((W_(1))/( 80) + ( W_(2))/( 28))`
`( W_(1))/( 80) = ( W_(2))/( 28)`
`( W_(1))/( W_(2)) = ( 80)/( 28) = ( 20)/( 7)`