DP Chemistry (first assessment 2025)

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Question 21M.2.SL.TZ2.d

Date	May 2021	Marks available	[Maximum mark: 3]	Reference code	21M.2.SL.TZ2.d
Level	SL	Paper	2	Time zone	TZ2
Command term	Justify, Suggest	Question number	d	Adapted from	N/A

d.

[Maximum mark: 3]

21M.2.SL.TZ2.d

Suggest, giving reasons, the relative volatilities of SCl₂ and H₂O.

[3]

Markscheme

H₂O forms hydrogen bonding «while SCl₂ does not» ✓

SCl₂ «much» stronger London/dispersion/«instantaneous» induced dipole-induced dipole forces ✓

Alternative 1:
H₂O less volatile AND hydrogen bonding stronger «than dipole–dipole and dispersion forces» ✓

Alternative 2:
SCl₂ less volatile AND effect of dispersion forces «could be» greater than hydrogen bonding ✓\

Ignore reference to Van der Waals.

Accept “SCl₂ has «much» larger molar mass/electron density” for M2.

Syllabus sections

Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.6—Molecular polarity depends on both bond polarity and molecular geometry. Deduce the net dipole moment of a molecule or ion by considering bond polarity and molecular geometry.

Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.9—Given comparable molar mass, the relative strengths of intermolecular forces are generally: London (dispersion) forces < dipole–dipole forces < hydrogen bonding. Explain the physical properties of covalent substances to include volatility, electrical conductivity and solubility in terms of their structure.