Which of the following is used in preparation of hydrogen peroxide by Merck process?

$$ \begin{aligned} &\text { Identify ' } \mathrm{A} \text { ' in the following reaction. }\\ &\underset{\text { (excess) }}{\mathrm{A}}+\underset{\text { (excess) }}{\operatorname{Acetyl} \text { chloride }} \xrightarrow[\mathrm{AlCl}_3]{\text { Anhydrous }} \end{aligned} $$

2-Chloroacetophenone + 4-Chloroacetophenone

The vapour density of a certain gas is 16 . What is the volume occupied by 8 g of gas at STP assuming ideal behaviour?

For the cell involving following reaction.

$$ \mathrm{Zn}_{(\mathrm{s})}+\mathrm{Ni}_{(\mathrm{aq})}^{+2} \longrightarrow \mathrm{Zn}_{(\mathrm{aq})}^{+2}+\mathrm{Ni}_{(\mathrm{s})}, \mathrm{E}_{\mathrm{cell}}^*=0.5 \mathrm{~V} . $$

What is standard Gibb's energy change of cell reaction?