How long should aqueous NaCl be electrolysed by passing 100 ampere current, so that 0.5 mol chlorine is released at anode?

Calculate the number of atoms present in 1.58 g metal if it forms bcc structure.

$$\left[\rho \times \mathrm{a}^3=1.58 \times 10^{-22} \mathrm{~g}\right]$$

Identify the correct order of thermal stability of hydrides of 16 group elements from the following.

Calculate the longest wavelength in hydrogen emission spectrum of Lyman series. $$\left(\mathrm{R}_{\mathrm{H}}=109677 \mathrm{~cm}^{-1}\right)$$