Question:
Consider the complete combustion of butane, the amount of butane utilized to produce $72.0 \mathrm{~g}$ of water is ________$\times 10^{-1} \mathrm{~g}$. (in nearest integer)
Solution:
$\mathrm{C}_{4} \mathrm{H}_{10}+\frac{13}{2} \mathrm{O}_{2} \longrightarrow 4 \mathrm{CO}_{2}+5 \mathrm{H}_{2} \mathrm{O}$
Moles of $\mathrm{H}_{2} \mathrm{O}=\frac{72}{18}=4$
Moles of $\mathrm{C}_{4} \mathrm{H}_{10}$ used $=\frac{1}{5} \times 4$
Weight of $\mathrm{C}_{4} \mathrm{H}_{10}$ used $=\frac{4}{5} \times 58$
$=46.4 \mathrm{gm}$