Question

Which of the following pairs of cations can be separated by adding $N{H}_{4}Cl,N{H}_{4}OH$ and then
$(N{H}_4{)}_{2}C{O}_3$ to the mixture?

• A. $C{a}^{2+},M{g}^{2+}$
• B. $B{a}^{2+},S{r}^{2+}$
• C. $S{r}^{2+},C{a}^{2+}$
• D. $B{a}^{2+},C{a}^{2+}$

Answer 1

Answer: (A)

$C{a}^{2+},M{g}^{2+}$

The sparingly soluble carbonates derived from $C{a}^{2+},S{r}^{2+}$ and $B{a}^{2+}$ ions are precipitated by the addition of ammonia carbonate, $(N{H}_4{)}_{2}C{O}_3$ solution in presence of $N{H}_{4}OH$ and $N{H}_{4}CI$.

Carbonate $K_{SP}$ at ${25}^{\circ }C$

$CaC{O}_3$ $4.7\times {10}^{-9}$

$SrC{O}_3$ $7\times {10}^{-10}$

$BaC{O}_3$ $1.6\times {10}^{-9}$