Question

Assuming the mass of the earth as $\text{6.64}\times 10^{24} \, kg$ and the average mass of the atoms that make up the earth as $40 \, u$ (atomic mass unit), the number of atoms in the earth is approximately

• A. $10^{30}$
• B. $10^{40}$
• C. $10^{50}$
• D. $10^{60}$

Answer 1

Answer: (C)

$1a.m.u=1u=\text{1.6} \, \times \, 10^{- 27} \, kg$
$40u=40\times \text{1.6}\times 10^{- 27} \, kg$
Number of atoms in earth,
$=\frac{6.64 \, \times \, 10^{24}}{40 \, \times 1.6 \, \times 10^{- 27}}$ = $10^{50}$