The amount of ${\mathrm{CO}}_2$ produced when 45 g of ethane is treated with 3.5 mole of ${\mathrm{O}}_2$ $\left(2{\mathrm{C}}_2{\mathrm{H}}_6+7{\mathrm{O}}_2\to 4{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}\right) is$

$2{\mathrm{C}}_2{\mathrm{H}}_6+7{\mathrm{O}}_2\to 4{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}$

2 moles → 7 moles → 4 moles

$60\mathrm{g}--32\times 7\mathrm{g}--4\times 44\mathrm{g}$

45 g ––––– 3.5 mole –––– ?

For 45g of ethane 5.25 moles ${\mathrm{O}}_2$ required.

Hence ${\mathrm{O}}_2$ is limiting reagent.

$\mathrm{Wt} {\mathrm{CO}}_2=4\times 44\times \frac{3.5}{7}=88\mathrm{g}$