Edexcel IAL Chemistry 7.2 Hydrogen-bond interactions

Show the donor H attached to N, O or F, aim the dotted attraction at a lone pair on another molecule and add the relevant partial charges and angle.

Exam points

Draw hydrogen bonds from a lone pair to a δ+ H with the required molecular alignment.
Explain anomalous HF or NH₃ boiling points by identifying intermolecular hydrogen bonds.

[Maximum number: 1]

This question is about hydrogen bonding.

Which diagram best represents a hydrogen bond between two water molecules?
□ A

Figure for Question 7.2—The interactions in molecules, such as H2O, liquid NH3 and liquid HF, which give rise to hydrogen bonding question 1 — Edexcel A-Level Chemistry AS

□ B

□ C

□ D

Figure for Answer to Question 7.2—The interactions in molecules, such as H2O, liquid NH3 and liquid HF, which give rise to hydrogen bonding question 1 — Edexcel A-Level Chemistry AS

The only correct answer is A

B is not correct because the 2 water molecules do not form a hydrogen bond between two hydrogen atoms

C is not correct because the hydrogen bond angle is not $104.5^{\circ}$

D is not correct because the angle between 2 water molecules should be $180^{\circ}$ and water molecules should not have a bond angle of $180^{\circ}$

(1)

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7.2—The interactions in molecules, such as H2O, liquid NH3 and liquid HF, which give rise to hydrogen bonding question 1