Which of the following compounds are partially soluble or insoluble in $NH_4OH$ solution?
$(I)$ $Fe(OH)_3$
$(II)$ $Ag_2CrO_4$
$(III)$ $Al(OH)_3$
$(IV)$ $Ag_2CO_3$

What would happen when a solution of potassium chromate is treated with an excess of dilute nitric acid?

$HgCl_2$ and $I_2$ both when dissolved in water containing $I^{-}$ ions,the pair of species formed is

$A$ solution of $0.1 \ M$ weak base $(B)$ is titrated with $0.1 \ M$ of a strong acid $(HA)$. The variation of $pH$ of the solution with the volume of $HA$ added is shown in the figure below. What is the $pK_{b}$ of the base? The neutralization reaction is given by $B + HA \rightarrow BH^{+} + A^{-}$.

In which of the following mixed aqueous solutions,$pH = pK_{a}$ at equilibrium?
$(1)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ CH_{3}COONa$
$(2)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 50 \ mL$ of $0.1 \ M \ NaOH$
$(3)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ NaOH$
$(4)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ NH_{3}$

The hydrolysis constants of salts $M_1X$ and $M_2X$ formed from a strong acid and weak bases are $10^{-7}$ and $10^{-4}$ respectively. For base $M_3OH$,$K_b = 10^{-4}$. The decreasing order of basic strength is: