Multiple choice

Equal weights of $CH_{4}$ and $H_{2}$ are mixed in an empty container at $25^{\circ}C$. The fraction of the total pressure exerted by $H_{2}$ is:

  1. $1/9$
  2. $1/2$
  3. $8/9$
  4. $16/17$
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C Correct answer
Explanation

Equal weights means let mass be w. Moles of CH4 = w/16, moles of H2 = w/2. Mole fraction of H2 = (w/2) / (w/2 + w/16) = (8w/16) / (9w/16) = 8/9. The partial pressure fraction equals the mole fraction.

AI explanation

Assume 16 g of methane (molar mass 16) and 16 g of hydrogen (molar mass 2) are added to the container. Methane constitutes 1 mole, while hydrogen constitutes 8 moles. The fraction of total pressure exerted by a gas equals its mole fraction, which is the moles of hydrogen divided by the total moles. Calculate 8 divided by (1+8) to find the fraction of the total pressure exerted by hydrogen is 8/9.

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