The number of hydrogen atoms in 45 g glucose, C₆H₁₂O₆, is:

Moles of glucose = 45/180 = 0.25 mol. Each molecule contains 12 H atoms. Moles of H atoms = 0.25 × 12 = 3 mol. H atoms = 3 × 6.022 × 10²³ ≈ 1.8 × 10²⁴.