The number of water molecules in $1 \ L$ of water is

Two flasks $A$ and $B$ of $500 \ mL$ each are filled with $O_2$ and $SO_2$ respectively at $300 \ K$ and $1 \ atm$ pressure. Then the flasks contain:

The number of neutrons in $5 \ g$ of $D_2O$ ($D$ is $_1^2H$) are ................ $N_A$.

$K-40$ is a natural radioactive isotope which constitutes $0.012\%$ of natural potassium. If a cup of milk contains $370 \ mg$ of $K$,how many atoms of $K-40$ are ingested?

How many electrons are present in $2 \times 10^{-3} \ mol$ of ${}_{8}^{18}O^{2-}$?

What is the number of moles of water molecules present in a mole of carnallite?