Question

A 1 : 1 mixture (by weight) of hydrogen and helium is enclosed in a one litre flask kept at O°C. Assuming ideal behavior, the partial pressure of helium is found to be 0.42 atm. Then the concentration of hydrogen would be

(a) 0.0375 M

(b) 0.028 M

(c) 0.0562 M

(d) 0.0187 M

Answer 1

Correct option is (a) 0.0375 M

1:1 mixture by weight of H₂ and He means if 4 g each of He and H₂ are taken, 1 mole of He is present then number of moles of H₂ will be 2.

According to Dalton's law of partial pressure p_T = p₁ + p₂

Using, p_T , total number of moles(n) can be found out T

1.26 = n x 0.0821 x 273

n = 0.0562

Number of moles of H₂ = n₂ = 2/3 x 0.0562 = 0.0375 mol

Volume = 1 L Therefore,

concentration of H₂ = 0.0375 M