Assertion (A): Acetic acid but not formic acid can be halogenated in presence of red $$\mathrm{P}$$ and $$\mathrm{Cl}_2$$.

Reason (R): Acetic acid is a weaker acid than formic acid.

Assertion (A): Trans $$\left[\mathrm{Cr} \mathrm{Cl}_2(\mathrm{ox})_2\right]^{3-}$$ shows optical isomerism.

Reason (R): Optical isomerism is common in octahedral complexes involving bidentate ligands.

(a) (i) What should be the signs (positive/ negative) for $$\mathrm{E}_{\text {Cell }}^0$$ and $$\Delta \mathrm{G}^0$$ for a spontaneous redox reaction occurring under standard conditions?

(ii) State Faraday's first law of electrolysis.

OR

(b) Calculate the emf of the following cell at $$298 \mathrm{~K}$$ :

$$\begin{aligned} & \mathrm{Fe}_{(\mathrm{s})}\left|\mathrm{Fe}^{2+}(0.01 \mathrm{M}) \| \mathrm{H}_{(1 \mathrm{M})}^{+}\right| \mathrm{H}_{2(\mathrm{~g})}(1 \mathrm{bar}), \mathrm{Pt}_{(\mathrm{s})} \\ & \text { Given } \mathrm{E}_{\mathrm{Cen}}^0=0.44 \mathrm{~V}. \end{aligned}$$

What happens to the rate constant $$k$$ and activation energy $$E_a$$ as the temperature of a chemical reaction is increased? Justify.