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.
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