Question

determine the mass of oxygen in a 5.8-g sample of sodium bicarbonate (nahco₃). express your answer in grams of oxygen to two significant figures.

Explanation:

Step1: Calculate molar mass of NaHCO₃

Molar masses: Na=23, H=1, C=12, O=16.
Molar mass = 23 + 1 + 12 + (3×16) = 84 g/mol.

Step2: Find mass fraction of O

Mass of O in 1 mol NaHCO₃ = 3×16 = 48 g.
Fraction = $\frac{48}{84}$ ≈ 0.5714.

Step3: Compute O mass in sample

O mass = 5.8 g × 0.5714 ≈ 3.314 g ≈ 3.3 g (2 sig figs).

Answer:

3.3 g O