Question

If calcium salt of anion has formula ${\mathrm{Ca}}_3{\mathrm{X}}_2$, what is the valency of $\mathrm{X}$ ? Write the formula of (I) sodium salt of X and (ii) aluminium salt of X.

Answer 1

1. The calcium salt of the anion has a molecular formula ${\mathrm{Ca}}_3{\mathrm{X}}_2$, the valency of $\mathrm{X}$can be determined by applying the criss-cross method:

$$\begin{gathered} \mathrm{Symbol}\mathrm{Ca}\mathrm{X} \\ \searrow \swarrow \\ \mathrm{Valency}23 \end{gathered}$$

Thus, by applying criss-cross method,valency of $\mathrm{X}$ comes out to be $3$.

2. The sodium salt of $\mathrm{X}$ will be

$$\begin{gathered} \mathrm{Symbol}\mathrm{Na}\mathrm{X} \\ \searrow \swarrow \\ \mathrm{Valency}13 \end{gathered}$$

Thus,by applying criss-cross method , the molecular formula of sodium salt of $\mathrm{X}$ will be ${\mathrm{Na}}_3\mathrm{X}$.

3. The aluminum salt of $\mathrm{X}$:

$$\begin{gathered} \mathrm{Symbol}\mathrm{Al}\mathrm{X} \\ \searrow \swarrow \\ \mathrm{Valency}33 \end{gathered}$$

Thus, by applying criss-cross method , the molecular formula of aluminium salt of $\mathrm{X}$ will be $\mathrm{AlX}$.

Hence, the valency of X is 3 and the formula of (i) ${\mathrm{Na}}_3\mathrm{X}$and (ii)$\mathrm{AlX}$