Question

Calculate the number of moles, molecules and total number of atoms present in $0.49$ g of helium gas.
[Given: $C=12,O=16,N=14,H=1,He=4$]

Answer 1

(i) Moles of Helium gas (n)= $\frac{mass}{molarmassofHe}$

$\Rightarrow n=\frac{0.49}{4}=0.122mol$

(ii) Number of molecules= n $\times$ Avogadro's number

$=0.122\times 6.022\times {10}^{23}$

$=7.22\times {10}^{22}$

(iii) Number of atoms= Number of molecule in Helium

As, Helium is monoatomic.