Concentration of $H _2 SO _4$ and $Na _2 SO _4$ in a solution is $1 M$ and $1.8 \times 10^{-2} M$, respectively. Molar solubility of $PbSO _4$ in the same solution is $X \times 10^{- Y } M$ (expressed in scientific notation). The value of $Y$ is. . . .

[Given: Solubility product of $PbSO _4\left(K_{s p}\right)=1.6 \times 10^{-8}$. For $H _2 SO _4, K_{a l}$ is very large and $\left.K_{a 2}=1.2 \times 10^{-2}\right]$

The solubility of $Ba_3(AsO_4)_2$ (molar mass $= 690$) is $6.9 \times 10^{-2} \,g/100\, mL$. What is the value of its $K_{sp}$?

In an aqueous solution $SCN^{-1}, B^{-1}, I^{-1}$ and $Cl^-$ are present. Which will get precipitated first, when $AgNO_3$ is mixed with each of them? Given that 
$Ksp$ of $AgCl = 1.2 \times 10^{-10}$,
$Ksp$ of $AgI = 1.7 \times 10^{-16}$
$Ksp$ of $AgSCN = 7.1 \times 10^{-7}$,
$Ksp$ of $AgBr = 3.5 \times10^{-13}$

Calculate the molar solubility of $Ni ( OH )_{2}$ in $0.10 \,M$ $NaOH$. The ionic product of $Ni ( OH )_{2}$ is $2.0 \times 10^{-15}$

The solubility product of $BaS{O_4}$ is $1.3 \times {10^{ – 9}}$. The solubility of this salt in pure water will be