Question

If one atom of an element $A$ weighs $6.644\times 10^{-23}g$, then number of gram-atoms in $20kg$ of it is

• A. 500
• B. 20
• C. 1000
• D. 2000

Answer 1

Answer: (A)

Atomic weight of $A$

= weight of one atom $\times$ Avogadro's constant

$=6.644\times 10^{-23}\times 6.023\times 10^{23}=40g$

Number of gram-atoms (moles) in $20kg$

$=\frac{\text{ weight in }g}{\text{ atomic weight }}=\frac{20\times 1000}{40}=500$