Question

How many helium atoms are present in 80 g of helium?

• A. $12.044\times {10}^{23}$
• B. $12.044\times {10}^{21}$
• C. $12.044\times {10}^{22}$
• D. $12.044\times {10}^{24}$

Answer 1

The correct option is D $12.044\times {10}^{24}$

Gram atomic mass of helium = 4g
Number of moles$=\frac{GivenMass}{GramAtomicMass}$

$\therefore$Number of moles in 80g$=\frac{80}{4}=20$
1 mole contains $6.022\times {10}^{23}$ atoms.
$\therefore$ Number of atoms in 20 moles of helium $=20\times 6.022\times {10}^{23}$
$=12.044\times {10}^{24}$