DP Chemistry (first assessment 2025)

Question 19N.2.SL.TZ0.a(iv)

Date	November 2019	Marks available	[Maximum mark: 2]	Reference code	19N.2.SL.TZ0.a(iv)
Level	SL	Paper	2	Time zone	TZ0
Command term	Suggest	Question number	a(iv)	Adapted from	N/A

a(iv).

[Maximum mark: 2]

19N.2.SL.TZ0.a(iv)

Suggest why water vapour deviates significantly from ideal behaviour when the gases are cooled, while nitrogen does not.

[2]

Markscheme

Any two of:
nitrogen non-polar/London/dispersion forces AND water polar/H-bonding ✔
water has «much» stronger intermolecular forces ✔
water molecules attract/condense/occupy smaller volume «and therefore deviate from ideal behaviour» ✔

Syllabus sections

Structure 1. Models of the particulate nature of matter » Structure 1.5—Ideal gases » Structure 1.5.2—Real gases deviate from the ideal gas model, particularly at low temperature and high pressure. Explain the limitations of the ideal gas model.

Question 19N.2.SL.TZ0.a(iv)

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Syllabus sections

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