Calculate the formula unit masses of $ZnO, Na_2O, K_2CO_3$ given atomic masses of $Zn=65\,u, Na=23\,u, K=39\,u, C=12\,u$ and $O=16\,u$.

Calculate the molecular masses of $C_2H_4$,$NH_3$ and $CH_3OH$.

One mole of $H_{2}O$ means:
$(i)$ $18 \text{ g}$ of $H_{2}O$
$(ii)$ $6.022 \times 10^{23}$ molecules of $H_{2}O$
$(iii)$ $180 \text{ g}$ of $H_{2}O$
$(iv)$ $1.8 \text{ g}$ of $H_{2}O$

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.

$A$ silver ornament of mass $m \, g$ is polished with gold equivalent to $1\%$ of the mass of silver. Compute the ratio of the number of atoms of gold and silver in the ornament.

Which has more number of atoms?
$(i)$ $100 \, g$ of $N_2$
$(ii)$ $100 \, g$ of $NH_3$