Question

Calculate the number of moles of the following:

(i) 52 g of He (ii) 12·044 x ${10}^{23}$ atoms of He

Answer 1

Explanation of Part 1:

We know that :

• Number of moles=$\frac{givenmass}{molarmass}$
• Molar mass of $\mathrm{He}$=4 g
• Given mass of Helium =52 g
• So, ${\mathrm{n}}_{\mathrm{He}}$=$\frac{1}{4}\times 52=13moles$
• Therefore,the number of moles of 52 g of $\mathrm{He}$ are 13.

Explanation of Part 2:

$6.022\times {10}^{{23}_{}}atomsofHe=1molofHe$

$12.044\times {10}^{23}AtomsofHelium=\frac{12.044\times {10}^{23}}{6.044\times {10}^{23}}$$=2\mathrm{mole}$