Question

One atom of an element $x$ weigh $x=6.643\times 10^{-23}g$. Number of moles of atom in $20kg$ is :

• A. $4$
• B. $40$
• C. $100$
• D. $500$

Answer 1

Answer: (D)

Atomic weight of an element
$x=6.643\times 10^{-23}\times N_A=40$
no. of moles of $x=\frac{20\times 1000}{40}=500$