Question

Mass of one atom of $X$ is $6.66\times {10}^{-23}$ g. Hence, number of mole of atom $X$ in $40$ kg is :

• A. ${10}^3$ mol
• B. ${10}^{-3}$ mol
• C. $\frac{40\times {10}^3}{6.66\times {10}^{-23}}$ mol
• D. $\frac{40\times {10}^3}{6.022\times {10}^{23}}$ mol

Answer 1

The correct option is A ${10}^3$ mol

Mass of one atom $=6.66\times {10}^{-23}g$
$\therefore$ Atomic mass$=6.66\times {10}^{-23}\times 6.02\times {10}^{23}$ $=40g$ $mo{l}^{-1}$
$\therefore$Number of moles in $40kg=\frac{40000}{40gmo{l}^{-1}}=1000mol$