Which of the following is sparingly soluble in cold water and fairly soluble in hot water?

Which of the following salts is insoluble in water at room temperature but soluble in boiling water?

Consider the following sequence of reactions:
$M^{2+}(aq.)$ $\xrightarrow{NH_4Cl(s) + (NH_4)_2CO_3 \, sol.} Q \downarrow$ $\xrightarrow[\text{Followed by addition of } (NH_4)_2C_2O_4]{CH_3COOH} R \downarrow$
Which of the following cations can form precipitate $Q$ but does not form precipitate $R$?

When calomel reacts with $NH_4OH$,we get

Sodium Carbonate cannot be used in place of $(NH_4)_2CO_3$ for the identification of $Ca^{2+}$,$Ba^{2+}$,and $Sr^{2+}$ ions (in group $V$) during mixture analysis because

Which ion is detected using Nessler's reagent?