How many moles of carbon(iv)oxide contains 16.0g of oxygen? [ C = 12.0, O = 16.0 ]

Analyze the question: We need the number of moles of CO₂ that contain 16.0 g of oxygen.

Concept: Each mole of CO₂ contains 2 moles of oxygen atoms (O), so the mass of oxygen in 1 mole of CO₂ is 2 × 16.0 = 32.0 g.

Solution:

1. Molar mass of CO₂ = 12.0 + (2 × 16.0) = 44.0 g/mol
2. Mass of oxygen in 1 mol of CO₂ = 32.0 g
3. Moles of CO₂ containing 16.0 g of oxygen:

moles = 16.0 g ÷ 32.0 g/mol = 0.50 mol

Check by another route: 16.0 g of oxygen atoms = 16.0 ÷ 16.0 = 1 mol of O atoms. Since each CO₂ has 2 O atoms, moles of CO₂ = 1 ÷ 2 = 0.50 mol.

Answer: 0.50 mol, which is option D.

Tip: Use the formula's atom ratio. When a question asks for moles of a compound containing a given mass of one element, first convert the mass to moles of that element, then divide by the number of atoms of that element in the formula (here, 2 for O in CO₂). Also, don't use the 44 g/mol molar mass here, since the question gives the mass of oxygen only, not the mass of CO₂.