Question

A gas mixture of 40% He and 60% Ne is passed through a diffusion tube and the product has 10% He and 90% Ne, what is the percentage of He recovered?

(a) 25%

(b) 33.3%

(c) 50%

(d) 66.6%

Answer 1

Correct choice is (b) 33.3%

Easiest explanation: Let the amount of input gas mixture be F, amount of He recovered be D. He balance: 0.4F = 1D + 0.1(F – D), => D/F = 0.333, => percentage of He recovered = 33.3%.