The shortest wavelength of H atom in the Lyman series is $$\lambda $$₁. The longest wavelength in the Balmar series of He⁺ is :

If the equilibrium constant for
A ⇌ B + C is $$K_{eq}^{(1)}$$ and that of
B + C ⇌ P is $$K_{eq}^{(2)}$$, the equilibrium
constant for A ⇌ P is :

The reaction in which the hybridisation of the underlined atom is affected is :

A test consists of 6 multiple choice questions, each having 4 alternative answers of which only one is correct. The number of ways, in which a candidate answers all six questions such that exactly four of the answers are correct, is __________.