Question

Equal weights of methane and oxygen are mixed in an empty container at 25°C. The fraction of the total pressure exerted by oxygen is

(a) 1/3

(b) 1/2

(c) 1/3 x 273/298

Answer 1

Correct option (a) 1/3

Explanation:

Let the weight be w g

Thus, moles of methane = w/16

Moles of oxygen = w/32

Total moles = w/16 + w/32 = 3w/32

Mole fraction of  oxygen = (w/32)/(3w/32) = 1/3

Partial pressure of oxygen

= total pressure x mole fraction  of O₂ = p x 1/3

Hence, the fraction of total pressure exerted by O₂ = 1/3