What is the concentration of $Ba^{2+}$ when $BaF_2$ $(K_{sp} = 1.0 \times 10^{-6})$ begins to precipitate from a solution that is $0.30 \, M \ F^{-}$?

Which of the following happens when $NH_{4}OH$ is added gradually to the solution containing $1 \ M \ A^{2+}$ and $1 \ M \ B^{3+}$ ions?
Given: $K_{sp}[A(OH)_{2}] = 9 \times 10^{-10}$ and $K_{sp}[B(OH)_{3}] = 27 \times 10^{-18}$ at $298 \ K$.

The values of $K_{sp}$ of $CaCO_{3}$ and $CaC_{2}O_{4}$ are $4.7 \times 10^{-9}$ and $1.3 \times 10^{-9}$ respectively at $25 \, ^oC$. If the mixture of these two is washed with water,what is the concentration of $Ca^{2+}$ ions in water $\dots \times 10^{-5} \, M$?

$25.0 \ mL$ of $0.050 \ M \ Ba(NO_3)_2$ is mixed with $25.0 \ mL$ of $0.020 \ M \ NaF$. The $K_{sp}$ of $BaF_2$ is $0.5 \times 10^{-6}$ at $298 \ K$. The ratio of $[Ba^{2+}][F^{-}]^2$ to $K_{sp}$ is $.......$. (Nearest integer)

Assign $A, B, C, D$ from the given type of reaction.
$AlCl_3 + 3NaOH \longrightarrow Al(OH)_3 \downarrow + 3NaCl$

$A$ precipitate is formed when: