Equal masses of methane and oxygen are mixed in empty container at 250?(C) The fraction of total pressure exerted by oxygen is___________________?
Correct answer: C. one / three
- A. one / seventeen
- B. sixteen / seventeen
- C. one / three
- D. two / three
Explanation
For equal masses, take 32 g of each gas: 32 g CH4 ÷ 16 g mol-1 = 2.0 mol CH4, while 32 g O2 ÷ 32 g mol-1 = 1.0 mol O2. At the same temperature and volume, pressure is proportional to moles, so the oxygen fraction is 1.0 mol ÷ (2.0 mol + 1.0 mol) = 1/3. The likely trap is 2/3, which is the methane fraction rather than the oxygen fraction.
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About Ideal Gas Equation
The ideal gas equation, PV = nRT, relates pressure, volume, amount and absolute temperature when gas particles are assumed to have negligible volume and no intermolecular forces. Applications include finding molar mass, density or an unknown gas variable, with careful use of Kelvin temperature and consistent units, and comparison with real-gas behaviour.
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