What is the numerical value of gas constant $R$ in terms of $\mathrm{L} \mathrm{atm} \mathrm{K}^{-1} \mathrm{~mol}^{-1}$ ?

What type of solid is the silica?

Which from following mixtures in water acts as a buffer?

Calculate van't Hoff factor of 0.15 M solution of electrolyte if it freezes at $-$0.5 K.

$$\left[\mathrm{K}_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$$