Question

The total number of electrons present in $18mL$. of water is .......................

Answer 1

Considering density of water to be $1.0g/mL,18mL$ of water is $18g(1.0mol)$ of water and it contain Avogadro number of molecules. Also one molecule of water contain
$2\times ($ one from each $H$-atom $)+8\times ($ from oxygen atom) $=10$ electrons.
$\Rightarrow 1.0$ mole of $H_{2}O$ contain $=10\times 6.023\times 10^{23}$
$=6.023\times 10^{24}$ electrons.