In the above reaction, left hand side and right hand side rings are named as '$$\mathrm{A}$$' and 'B' respectively. They undergo ring expansion. The correct statement for this process is:

The products formed in the above reaction are

The energy of an electron in the first Bohr orbit of hydrogen atom is $$-2.18 \times 10^{-18} \mathrm{~J}$$. Its energy in the third Bohr orbit is ____________.

$$\mathrm{KMnO}_{4}$$ is titrated with ferrous ammonium sulphate hexahydrate in presence of dilute $$\mathrm{H}_{2} \mathrm{SO}_{4}$$. Number of water molecules produced for 2 molecules of $$\mathrm{KMnO}_{4}$$ is ___________.