Equal masses of methane and oxygen are mixed in an empty container at `25^(@)C`. The fraction of total pressure exerted by oxygen is

Options

A. `(1)/( 3) xx ( 273)/( 298) `
B. `(1)/( 3)`
C. `(1)/(2)`
D. `(2)/(3)`

Answer

B

Explanation

Let the mass of methane and oxygen be x g each.
Moles of `CH_(4) = ( x )/( 16)`
Moles of `O_(2) = ( x )/( 32)`
Total moles `= ( x )/( 16) + ( x)/( 32) = ( 3x )/( 32)`
`p_(O_(2)) = p_("total") xx x_(O_(2))`
`( p_(O_(2)))/( p_("total")) = x_(2) = ((x)/( 32))/( (3x)/(32)) = ( 1)/( 3)`