In $3$ moles of ethane $(C_{2}H_{6})$,calculate the following:
$i.$ Number of moles of carbon atoms.
$ii.$ Number of moles of hydrogen atoms.
$iii.$ Number of molecules of ethane.

$i.$ $1$ mole of $C_{2}H_{6}$ contains $2$ moles of carbon atoms.
$\therefore$ Number of moles of carbon atoms in $3$ moles of $C_{2}H_{6} = 2 \times 3 = 6 \text{ moles}$.
$ii.$ $1$ mole of $C_{2}H_{6}$ contains $6$ moles of hydrogen atoms.
$\therefore$ Number of moles of hydrogen atoms in $3$ moles of $C_{2}H_{6} = 3 \times 6 = 18 \text{ moles}$.
$iii.$ $1$ mole of $C_{2}H_{6}$ contains $6.022 \times 10^{23}$ molecules of ethane.
$\therefore$ Number of molecules in $3$ moles of $C_{2}H_{6} = 3 \times 6.022 \times 10^{23} = 1.8066 \times 10^{24} \text{ molecules}$.