How many times is hydrogen lighter than a gas mixture, in which there are 5 argon atoms for every 10 helium atoms?

1. Let’s calculate the volume fractions of helium and argon in the mixture:

N (mixtures) = N (He) + N (Ar) = 10 + 5 = 15 atoms;

ϕ (He) = N (He): N (mixtures) = 10: 15 = 0.6667;

ϕ (Ar) = N (Ar): N (mixtures) = 5: 15 = 0.3333;

2. find the molar mass of the mixture and hydrogen:

M (mixtures) = ϕ (He) * Ar (He) + ϕ (Ar) * Ar (Ar);

M (mixtures) = 0.6667 * 4 + 0.3333 * 40 = 16 g / mol;

M (H2) = 2 g / mol;

3.Let us determine how many times hydrogen is lighter than the presented mixture:

M (mixtures): M (H2) = 16: 2 = 8.

Answer: 8 times.