Question

The moles of methane required to produce $81g$ of water after complete combustion is ____ $\times 10^{-2}$ mol. [nearest integer]

Answer 1

Answer: 225

$C{H}_4+2O_2\to C{O}_2+2H_{2}O$
POAC on $H$ atom
$n_{CH4}\times 4=n_{H2O}\times 2$
$n_{C{H}_4}=\frac{81}{18}\times 2\times \frac{1}{4}=\frac{81}{36}$
$n_{C{H}_4}=2.25$
$=225\times 10^{-2}$
Nearest Integers $=225$