A completely sealed container holds a mixture of dihydrogen () and dioxygen () at a total pressure o — States of Matter and Gaseous State Chemistry Question
Question
A completely sealed container holds a mixture of dihydrogen ($H_2$) and dioxygen ($O_2$) at a total pressure of $1.0\text{ bar}$. Chemical analysis reveals the mixture contains exactly $20\%$ by weight of dihydrogen. Calculate the precise partial pressure of dihydrogen in the mixture (in $\text{bar}$), and multiply your final answer by $10$.
Answer: 8
💡 Solution & Explanation
Assume a total mass of $100\text{ g}$. Mass of $H_2 = 20\text{ g}$, Mass of $O_2 = 80\text{ g}$. Moles of $H_2 = 20 / 2 = 10\text{ mol}$. Moles of $O_2 = 80 / 32 = 2.5\text{ mol}$. Total moles = $10 + 2.5 = 12.5\text{ mol}$. Mole fraction of $H_2 = 10 / 12.5 = 0.8$. Partial pressure of $H_2 = \chi_{H_2} \times P_{total} = 0.8 \times 1.0\text{ bar} = 0.8\text{ bar}$. Multiplying by 10 gives $8$.
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