Question

(a) Calculate the number of moles and the number of molecules present in 1.4 g of ethylene gas. What is the volume occupied by the same amount of ethylene?
(b) What is the vapour density of ethylene?

Answer 1

(a) The molecular weight of ethylene
= 12+2+12+2 =28g

$Mole=\frac{givenmass}{molarmass}=\frac{1.4}{28}=0.05moles$

Number of molecules in 1 mole = $6.023\times {10}^{23}$
Therefore,
Number of molecules in 0.05 mole = $6.023\times {10}^{23}\times 0.05=0.3\times {10}^{23}3\times {10}^{22}$ ​​​molecules.
Volume of occupied by 1 mole = 22.4l
volume of occupied by 0.05 = 22.4 $\times$ 0.05 = 1.12 litre

(b)