4 gram of NaOH is added in water to form 500 mL solution at 298 K . What is pH of solution? (Molar mass of $\mathrm{NaOH}=40 \mathrm{~g} \mathrm{~mol}^{-1}$ )

A compound contains atoms of $x, y$ and z elements. Oxidation numbers of $x, y$ and $z$ are +3 , +5 and -2 respectively. Identify the possible formula of this compound.

Which of the following compound is used for preparation of quicklime?

Which from following gases is adsorbed to greater extent if adsorbent remains same at similar conditions of temperature and pressure?