Assertion (A) Electron gain enthalpy becomes less negative as we go down a group.
Reason (R) Size of the atom increases on going down the group and the added electron would be farther away from the nucleus.
Assertion (A) Among the two $$\mathrm{O}-\mathrm{H}$$ bonds in $$\mathrm{H}_2 \mathrm{O}$$ molecule, the energy required to break the first $$\mathrm{O}-\mathrm{H}$$ bond and the other $$\mathrm{O}-\mathrm{H}$$ bond is same.
Reason (R) This is because the electronic environment around oxygen is the same even after breakage of one $$\mathrm{O}-\mathrm{H}$$ bond.
Assertion (A) : Nitration of benzene with nitric acid requires the use of concentrated sulphuric acid.
Reason (R) : The mixture of concentrated sulphuric acid and concentrated nitric acid produces the electrophile, NO$$_2^+$$.
Assertion (A) Beryllium carbonate is kept in the atmosphere of carbon dioxide.
Reason (R) Beryllium carbonate is unstable and decomposes to give beryllium oxide and carbon dioxide.