CAIE A-Level Chemistry 3.6.1 Hydrogen Bonding

Practise describing hydrogen bonds between N–H or O–H molecules and explaining the anomalous properties of water.

Exam points

describe attraction between a δ+ hydrogen bonded to N or O and a lone pair on N or O in another molecule
link high melting point, boiling point and surface tension to energy needed to overcome hydrogen bonds
explain ice’s lower density through an open hydrogen-bonded lattice that collapses partly on melting

[Maximum number: 1]

Oxygen is a Group 16 element.

Fig. 2.1 shows the boiling points of $\mathrm{H}_{2} \mathrm{O}$ and other Group 16 hydrides.

Fig. 2.1

Explain why the boiling point of $\mathrm{H}_{2} \mathrm{O}$ is much higher than that of $\mathrm{H}_{2} \mathrm{~S}$ .

(only) $\mathrm{H}_{2} \mathrm{O}$ has hydrogen bonding AND hydrogen bonding (much) stronger than the other intermolecular forces

OR

$\mathrm{H}_{2} \mathrm{O}$ has hydrogen bonding AND because of higher electronegativity of O compared to S

OR

stronger van der waals' forces because (only) $\mathrm{H}_{2} \mathrm{O}$ has hydrogen bonding

OR

hydrogen bond AND increased strength of permanent dipoles in $\mathrm{H}_{2} \mathrm{O}$ outweighs the increase in strength of id-id in the others

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3.6.1—Hydrogen bonding question 1