Cinnabar $(HgS)$ is a prominent ore of mercury. How many grams of mercury are present in $225 \,g$ of pure $HgS$ (in $,g$)? Molar mass of $Hg$ and $S$ are $200.6 \,g \,mol^{-1}$ and $32 \,g \,mol^{-1}$ respectively.

Which of the following contains the maximum number of molecules?

$(a)$ Define the following:
$(i)$ Mole
$(ii)$ Gram atomic mass
$(iii)$ Gram molecular mass
$(b)$ Calculate the mass of the following:
$(i)$ $2$ moles of carbon dioxide
$(ii)$ $6.022 \times 10^{23}$ molecules of carbon dioxide.

Verify by calculating that:
$(a)$ $5 \, mol$ of $CO_2$ and $5 \, mol$ of $H_2O$ do not have the same mass.
$(b)$ $240 \, g$ of calcium and $240 \, g$ of magnesium elements have a mole ratio of $3:5$.

Calcium chloride when dissolved in water dissociates into its ions according to the following equation:
$CaCl_{2}(aq) \rightarrow Ca^{2+}(aq) + 2Cl^{-}(aq)$
Calculate the number of ions obtained from $CaCl_{2}$ when $222 \, g$ of it is dissolved in water.

What is the fraction of the mass of water due to neutrons?