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.
Assertion (A) Separation of Zr and Hf is difficult.
Reason (R) Zr and Hf lie in the same group of the periodic table.