Which from the following is a correct stability order of complexes formed by metal ions if the ligand remains the same?

The stepwise stability constants of a complex are given below. What is its overall reaction stability constant $\beta_4$ ?
$M + L \rightleftharpoons ML ; K_1 = 1.0 \times 10^4$
$ML + L \rightleftharpoons ML_2 ; K_2 = 1.0 \times 10^3$
$ML_2 + L \rightleftharpoons ML_3 ; K_3 = 1.0 \times 10^3$
$ML_3 + L \rightleftharpoons ML_4 ; K_4 = 1.0 \times 10^2$
(Overall reaction : $M + 4L \rightleftharpoons ML_4$)

The reaction of $Pb(NO_3)_2$ and $NaCl$ in water produces a precipitate that dissolves upon the addition of $HCl$ of appropriate concentration. The dissolution of the precipitate is due to the formation of

Which one of the following has the highest molar conductivity?

Which of the following properties are exhibited by the $CN^-$ ion towards metal compounds?
$(a)$ Reducing
$(b)$ Oxidizing
$(c)$ Complexing

Urea reacts with water to form $A$ which will decompose to form $B$. $B$ when passed through $Cu^{2+}_{(aq)}$,a deep blue coloured solution $C$ is formed. What is the formula of $C$ from the following?