Multiple choice

Equal mass of $H_2$, $He$ and $CH_4$ are mixed in empty container at $300$K, when total pressure is $2.6$ atm. The partial pressure of $H_2$ in the mixture is:

  1. $2.1$ atm.
  2. $1.6$ atm.
  3. $0.8$ atm.
  4. $0.2$ atm.
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B Correct answer
Explanation

Equal mass m. Molar masses: H2=2, He=4, CH4=16. Moles: m/2, m/4, m/16. Total moles = m(8+4+1)/16 = 13m/16. Mole fraction of H2 = (m/2) / (13m/16) = 8/13. Partial pressure = (8/13) * 2.6 = 1.6 atm.

AI explanation

By Dalton's law of partial pressures, the partial pressure of a gas is proportional to its mole fraction. Assuming an equal mass of 16 grams for each gas, the moles of H2 are 8, the moles of He are 4, and the moles of CH4 are 1, yielding a total of 13 moles. The mole fraction of H2 is 8 divided by 13, which when multiplied by the total pressure of 2.6 atm gives a partial pressure of 1.6 atm.

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