DP Chemistry (first assessment 2025)

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Question 21M.2.HL.TZ1.7a(ii)

Date	May 2021	Marks available	[Maximum mark: 2]	Reference code	21M.2.HL.TZ1.7a(ii)
Level	HL	Paper	2	Time zone	TZ1
Command term	Discuss	Question number	a(ii)	Adapted from	N/A

a(ii).

[Maximum mark: 2]

21M.2.HL.TZ1.7a(ii)

(a(ii))

Discuss the relative length of the two O−O bonds in ozone.

[2]

Markscheme

both equal ✔

delocalization/resonance ✔

Accept bond length between 121 and 148 pm/ that of single O−O bond and double O=O bond for M1.

Syllabus sections

Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.2—Single, double and triple bonds involve one, two and three shared pairs of electrons respectively. Explain the relationship between the number of bonds, bond length and bond strength.

Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.11—Resonance structures occur when there is more than one possible position for a double bond in a molecule. Deduce resonance structures of molecules and ions.