DP Chemistry (first assessment 2025)

Question 19M.1A.HL.TZ1.17

Date	May 2019	Marks available	[Maximum mark: 1]	Reference code	19M.1A.HL.TZ1.17
Level	HL	Paper	1A	Time zone	TZ1
Command term		Question number	17	Adapted from	N/A

17.

[Maximum mark: 1]

19M.1A.HL.TZ1.17

Which equation represents the standard enthalpy of atomization of bromine, Br₂?

A. $\frac{1}{2}$ Br₂ (l) → Br (g)

B. Br₂ (l) → 2Br (g)

C. Br₂ (l) → 2Br (l)

D. $\frac{1}{2}$ Br₂ (l) → Br (l)

[1]

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One G2 comment asked if enthalpy of atomization was on the syllabus. This Topic 15.1 question was answered correctly by 54 % of candidates but did not differentiate well between higher and lower scoring candidates.

Syllabus sections

Reactivity 1. What drives chemical reactions? » Reactivity 1.2—Energy cycles in reactions » Reactivity 1.2.4—An application of Hess’s law uses enthalpy of formation data or enthalpy of combustion data to calculate the enthalpy change of a reaction. Calculate enthalpy changes of a reaction using ΔHf⦵ data or ΔHc⦵ data: ΔH⦵ = Σ ΔHf⦵products − Σ ΔHf⦵reactants ΔH⦵ = Σ ΔHc, ⦵reactants − Σ ΔHc. ⦵products

Question 19M.1A.HL.TZ1.17

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