Explain why water molecules form on average two hydrogen bonds per molecule, whereas ammonia molecules (NH3) form only one.
A hydrogen bond requires both a lone pair of electrons on a O, N or F atom and a hydrogen atom. In water there are two lone pairs and two hydrogen atoms, allowing the formation of two hydrogen bonds. In ammonia, although there are three hydrogen atoms, there is only one lone pair of electrons on the N, and this means that only one hydrogen bond can form per molecule.
Related Chemistry A Level answers
All answers ▸What does ‘aromatic’ mean?
Although carbon dioxide is a linear molecule it is still a greenhouse gas. Explain why that is.
What is Hess's law?
In the reaction CO(g) + 2H2(g) <--> CH3OH(g), explain why an increase in pressure increases the yield of methanol