Question

Atomic mass of Ca is not shown by

• A. 40
• B. 40 u
• C. 40 × 1.6 × 10^{-24} g
• D. 40 g

Answer 1

Answer: (D)

40 g

Answer 2

Atomic mass of Ca is given as 40 (dimensionless) or 40 u (atomic mass units). Writing it as $40 \times 1.6 \times 10^{-24}\, \mathrm{g}$ is an approximate conversion of u to grams (though the exact conversion factor is approximately $1.66 \times 10^{-24}\, \mathrm{g}$). However, expressing the atomic mass as 40 g is incorrect because 40 g represents the mass of 40 grams, not the mass of a single Ca atom.