If the actual mass of one atom of an element is 4.482 × 10⁻²³ g, what is its relative atomic mass?

Correct answer: b 27

Actual mass × Avogadro number = 4.482 × 10⁻²³ × 6.023 × 10²³ = 27 (Al).

Why the other options are wrong

• a 25: 25 would need one atom to weigh 4.15 × 10⁻²³ g; here 4.482 × 10⁻²³ × 6.023 × 10²³ = 27.
• c 29: 29 would need 4.82 × 10⁻²³ g; here the answer is 27.
• d 40: 40 (Ca) would need 6.64 × 10⁻²³ g; here the answer is 27.