Question

What is the mole fraction of O2 in a sample with 1.25 grams CH4, 45.2 grams N2, and 13.4 grams O2? a) 0.036 b) 0.100 c) 0.300 d) 0.500

Answer 1

To find the mole fraction of O2 in the sample, we first need to calculate the moles of each gas present in the sample.

1. Calculate moles of CH4:
Molar mass of CH4 (methane) = 12.01 g/mol (C) + 1.01 g/mol (H) × 4 = 16.05 g/mol
Moles of CH4 = 1.25 g / 16.05 g/mol ≈ 0.078 moles

2. Calculate moles of N2:
Molar mass of N2 (nitrogen) = 14.01 g/mol (N) × 2 = 28.02 g/mol
Moles of N2 = 45.2 g / 28.02 g/mol ≈ 1.613 moles

3. Calculate moles of O2:
Molar mass of O2 (oxygen) = 16.00 g/mol (O) × 2 = 32.00 g/mol
Moles of O2 = 13.4 g / 32.00 g/mol ≈ 0.419 moles

Now, we can find the total moles of gas in the sample:
Total moles = Moles of CH4 + Moles of N2 + Moles of O2
Total moles = 0.078 moles + 1.613 moles + 0.419 moles ≈ 2.110 moles

Finally, calculate the mole fraction of O2:
Mole fraction of O2 = Moles of O2 / Total moles
Mole fraction of O2 = 0.419 moles / 2.110 moles ≈ 0.198

So, the mole fraction of O2 in the sample is approximately 0.198. None of the given options match this result.