Which from following carbocations is least stable?

Identify compound Q in following reaction.

$$\mathrm{R}-\mathrm{OH}+\mathrm{Q} \longrightarrow \mathrm{R}-\mathrm{Cl}+\mathrm{HCl}+\mathrm{POCl}_3$$

A conductivity cell dipped on 0.05 M KCl has resistance 600 ohm. If conductivity is $0.0015 \mathrm{ohm}^{-1} \mathrm{~cm}^{-1}$. What is the value of cell constant?

Calculate ' $\alpha$ ' for 0.1 M acetic acid $\left(\mathrm{K}_{\mathrm{a}}=1.0 \times 10^{-5}\right)$