Identify the product ' $Z$ ' in the following series of reactions.

$$ \text { Ethanol } \xrightarrow[\Delta]{\mathrm{SOCl}_2} \mathrm{X} \xrightarrow[\text { Dry ether }]{\mathrm{Mg}} \mathrm{Y} \xrightarrow{\mathrm{NH}_3} \mathrm{Z} $$

Calculate the enthalpy of vaporisation of ethanol if 11.5 g of ethanol is completely vaporised by supplying 11.8 kJ of heat.

Identify the reagent involved in Sandmeyer reaction.

The solubility of AgBr is $7.1 \times 10^{-7} \mathrm{~mol} \mathrm{dm}^{-3}$. Calculate its solubility product at the same temperature.