$A$ and $B$ are two metals. The standard reduction potential of $A^{+}(a q) / A(s)$ and $B^{+}(a q) / B(s)$ are -0.5 V and +0.5 V respectively. What is the $\log K_c$ value for the following reaction at 298 K ?

$$ \begin{aligned} & A(s)+B^{+}(a q) \rightleftharpoons A^{+}(a q)+B(s) \\ & \left(\text { Given }: \frac{2.303 R T}{F}=0.06 \mathrm{~V}\right) \end{aligned} $$

For a zero order reaction $A \rightarrow$ product, a plot of $[A]$ (on $y$-axis) and time (on $x$-axis) gave a straight line with slope equal to $-3 \times 10^{-3} \mathrm{M} \mathrm{min}^{-1}$ and intercept equal to $2 \times 10^{-2} \mathrm{M}$ (on y -axis). What is the rate constant (in M $\mathrm{min}^{-1}$ ) of this reaction?

$$ \text { Match the following. } $$

$$ \begin{array}{llll} \hline & \text { List I } & & \text { List II } \\ \hline \text { A. } & \text { Negatively charged sol } & \text { I. } & \text { Emulsion } \\ \hline \text { B. } & \text { Milk } & \text { II. } & \text { Kala azar } \\ \hline \text { C. } & \text { Gold number } & \text { III. } & \begin{array}{l} \text { FeCl} \mathbf{C}_3 \text { solution is added to } \\ \text { excess NaOH solution } \end{array} \\ \hline \text { D. } & \text { Colloidal antimony } & \text { IV. } & \text { Protection of colloids } \\ \hline \end{array} $$

The correct answer is

$$ \begin{aligned} 4 \mathrm{Ag}(s)+8 \mathrm{CN}^{-}(a q) & +2 \mathrm{H}_2 \mathrm{O}(a q)+\mathrm{O}_2(g) \longrightarrow 4\left[\mathrm{Ag}(\mathrm{CN})_2\right]^{-}(a q)+4 \mathrm{OH}^{-}(a q) \end{aligned} $$

The above reaction represents the process of concentration of ore in the extraction of silver. The process is