Exercise: Finding Total Pressure-3

Question:

When 1 mole of methane gas (CH4) is burned at 450°C in the presence of
3 moles of oxygen gas (O2), carbon dioxide gas (CO2) and water vapors (H2O) are produced.
Assuming that all the methane is consumed in this process, calculate the following:
  1. What are the mole fractions of oxygen, carbon dioxide and water vapors in this case?
  2. Assuming the total pressure of the mixture of gases is 2.5 atm.,
    calculate the partial pressures of oxygen, carbon dioxide and water vapors.
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