200 mL of an aqueous solution of $\mathrm{HCl}(\mathrm{pH}=2)$ is mixed with 300 mL of aqueous solution of NaOH $(\mathrm{pH}=12)$ and is diluted to 1.0 L . The pH of the resulting solution is ( $\mathrm{pH}=2$ )

At $27^{\circ} \mathrm{C}, 100 \mathrm{~mL}$ of 0.5 M HCl is mixed with 100 mL of 0.4 M NaOH solution. To this resultant solution, 800 mL of distilled water is added. What is the pH of final solution?

At 298 K the molar solubility of $\mathrm{Cd}(\mathrm{OH})_2$ in $0.1 \mathrm{M} \mathrm{KOH}_{\mathrm{OH}}$ solution is $x \times 10^{-y}$. The values of $x$ and $y$ are respectively.

(At $298 \mathrm{~K}, K_{s p}$ of $\mathrm{Cd}(\mathrm{OH})_2=2.5 \times 10^{-14}$ )

Which of the following does not form a buffer solution?