What are the conditions for hydrogen bonding?

Water is a liquid while hydrogen sulphide is a gas. Explain.

Out of NH₃ and PH₃, which has higher boiling point and why?

Nitrogen and chlorine have the same electronegativity but only former shows intermolecular hydrogen bonding. Discuss.

Why does ice float over water?

Give reasons for the following:
(i) The density of water is maximum at 277 K (4°C).

(ii) Why glycerol (glycerine) is more viscous than ethyl alcohol?

Calcualte the total pressure in a mixture of 8 g of dioxygen and 4 g of dihydrogen confined in a vessel of 1 dm³ at  . R = 0.083 bar dm³ K^-1 mol^-1.

A mixture of dihydrogen and dioxygen at one bar pressure contains 20% by weight of dihydrogen. Calculate the partial pressure of dihydrogen.

Which among the following gases can be liquified easily?

• Chlorine

• Nitrogen

• Oxygen

• Hydrogen

180.

If average velocity of a sample of gas molecules at 300 K is 5 cm s^-1, what is RMS velocity of same sample of gas molecules at the same temperature? (Given, α: u: v = 1:1.224: 1.127)

• 6.112 cm/s

• 4.605 cm/s

• 4.085 cm/s

• 5.430 cm/s