An ideal gas mixture of $\mathrm{C}_2 \mathrm{H}_6$ and $\mathrm{C}_2 \mathrm{H}_4$ occupies a volume of 28 L at 1 atm and 273 K . This mixture reacts completely with 128 g of $\mathrm{O}_2$ to produce $\mathrm{CO}_2$ and $\mathrm{H}_2 \mathrm{O}(l)$. What is the mole fraction of $\mathrm{C}_2 \mathrm{H}_4$ in the mixture ?

Complete combustion of ethane gives only gaseous products. In a closed vessel, 15 g of ethane and 112 g of $\mathrm{O}_2$ were allowed to completely react. What is the total number of moles of gaseous substances present in the vessel at the end of the reaction?

Consider the following

(A) 0.0025

(B) 500.0

(C) 2.0034

Number of significant figures in $A, B$ and $C$ respectively, are