The ratio of wave length of photon corresponding to the alpha-line of Lyman series in H-atom and Beta-line of Balmer series in He+ is

The shortest wavelength of He+ ion in Balmer series is x, then longest wavelength in the Paschene series of Li+2 is

The ratio of difference in wavelengths of 1st and 2nd lines of Lyman series in H like atom to difference in wavelength for 2nd and 3rd lines of same series is:

Liquid ammonia bottle is cooled before opening the seal. Explain.

Liquid ammonia bottle contains the gas under very high pressure. If the bottle is opened as such, then the sudden decrease in pressure will lead to a large increase in the volume of the gas. As a result, the gas will come out of the bottle all of a sudden with force. This will lead to the breakage of the bottle and also some serious accident. However, if the bottle is cooled under tap water for sometime, this will lead to a decrease in the volume of the gas to a large extent. If the seal is opened now, the gas will come out of the bottle at a slow rate, thus, reducing the chances of accident.

The molecular speeds of gaseous molecules are analogous to those of rifle bullets; why is then odour of the gaseous molecule not detected so fast?

No, doubt molecules in the gaseous state move almost with the speed of rifle bullets. But these molecules donot follow a straight path. Since they undergo collisions with one another at a very fast rate, the path followed is zig-zag. Thus, the odour cannot be detected at the same speed at which the molecules move.