Q. One atom of an element $X$ weight 6.643$\times 10^{- 23}$g. number of moles of atom in 20 kg is
A) 140
B) 150
C) 250
D) 500
Explanation
(d)
Atomic weight of the element
$X = 6.643 \times 10^{- 23} \times N_{A} = 40$
No. of moles of $X = \frac{20 \times 1000}{40} = 500$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.