Question

Which solid will precipitate first if an aqueous solution of $N{a}_{2}Cr{O}_4$ at ${25}^o$C is slowly added to an aqueous solution containing $0.001MPb(N{O}_3{)}_2$ and $0.100MBa(N{O}_3{)}_2$ at ${25}^o$C?

• A. $BaCr{O}_4\left(s\right)$
• B. $NaN{O}_3\left(s\right)$
• C. $PbCr{O}_4\left(s\right)$
• D. $Pb\left(N{O}_3{)}_2\right(s)$
• E. none of these

Answer 1

The correct option is C $PbCr{O}_4\left(s\right)$

All sodium salts are soluble in water. Hence, sodium nitrate is soluble in water
All nitrates are soluble in water. Hence, lead nitrate is soluble in water.
The values of the solubility products of barium chromate and lead chromate are $2.2\times {10}^{10}$ and $2.0\times {10}^{16}$ respectively.
Hence, lead chromate will precipitate first.