The ratio of the shortest wavelength of two spectral series of hydrogen spectrum is found to be about 9. The spectral series are :

Compound A(C₉H₁₀O) shows positive iodoform test. Oxidation of A with KMnO₄/KOH given acid B(C₈H₆O₄). Anhydride of B is used for the preparation of phenolphthalein. Compound A is:

The major product 'Y' in the following reactions is :

For the reaction of H₂ with I₂, the rate constant is 2.5 × 10^–4 dm³ mol^–1s^–1 at 327°C and 1.0 dm³ mol^–1 at 527°C. The activation energy for the reaction, in kJ mole^–1 is : (R = 8.314 JK^–1 mol^–1 )