In the Solvay ammonia process,what causes the precipitation of sodium bicarbonate?

In the analysis of $III$ group basic radicals of salts,the purpose of adding $NH_4Cl_{(s)}$ to $NH_4OH$ is

Define the common ion effect and explain it with an example.

On addition of ammonium chloride to a solution of ammonium hydroxide,what happens to the concentration of $OH^{-}$ ions?

We have taken a saturated solution of $AgBr$. The $K_{sp}$ of $AgBr$ is $12 \times 10^{-14}$. If $10^{-7} \ mol$ of $AgNO_3$ are added to $1 \ L$ of this solution,find the conductivity (specific conductance) of this solution in terms of $10^{-7} \ S \ m^{-1}$ units.
Given: $\lambda^{\circ}_{(Ag^{+})} = 6 \times 10^{-3} \ S \ m^2 \ mol^{-1}$,$\lambda^{\circ}_{(Br^{-})} = 8 \times 10^{-3} \ S \ m^2 \ mol^{-1}$,$\lambda^{\circ}_{(NO_3^-)} = 7 \times 10^{-3} \ S \ m^2 \ mol^{-1}$.

Assertion : $Sb_2S_3$ is not soluble in yellow ammonium sulphide. Reason : The common ion effect due to $S^{2-}$ ions reduces the solubility of $Sb_2S_3$.