Question

A and B are ideal gases. The molecular weights of A and B are in the ratio of 1 : 4. The pressure of a gas mixture containing equal weights of Aand B is P atm. What is the partial pressure (in atm.) of B in the mixture

• A. P/5
• B. P/2
• C. P/2.5
• D. 3P/4

Answer 1

Answer: (A)

P/5

Answer 2

Let $M_A$ = a and $M_B$ = 4a
$w_A = w_B = m(say)$
$x_B = \frac{m/4a}{m/4a + m/a} = \frac{1}{5}$
$P_B = x_B \times P_{total} = P/5$