DP Chemistry (first assessment 2025)

Question 22M.2.HL.TZ2.5

Date	May 2022	Marks available	[Maximum mark: 5]	Reference code	22M.2.HL.TZ2.5
Level	HL	Paper	2	Time zone	TZ2
Command term	Calculate, Describe, Explain, State	Question number	5	Adapted from	N/A

[Maximum mark: 5]

22M.2.HL.TZ2.5

Iron(II) disulfide, FeS₂, has been mistaken for gold.

(a(i))

State the full electronic configuration of Fe²⁺.

[1]

Markscheme

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ ✔

Examiners report

Mostly well done which was a pleasant surprise since this is not overly easy, predictably some gave [Ar] 4s² 3d⁴.

(a(ii))

Explain why there is a large increase from the 8th to the 9th ionization energy of iron.

[2]

Markscheme

Any two of:

IE₉: electron in lower energy level
OR
IE₉: more stable/full electron level ✔

IE₉: electron closer to nucleus
OR
IE₉: electron more tightly held by nucleus ✔

IE₉: less shielding by «complete» inner levels ✔

Examiners report

Despite some confusion regarding which sub-level the electrons were being removed from, many candidates were able to make at least one valid point, commonly in terms of lower energy/ full sub level/closer to nucleus.

(b)

Calculate the oxidation state of sulfur in iron(II) disulfide, FeS₂.

[1]

Markscheme

–1 ✔

Accept “– I”.

Examiners report

This was an easy question, yet 30% of the candidates were unable to work it out; some wrote the oxidation state in the conventionally incorrect format, 1- and lost the mark.

(c)

Describe the bonding in iron, Fe (s).

[1]

Markscheme

electrostatic attraction/hold between «lattice of» positive ions/cations AND delocalized «valence» electrons ✔

Examiners report

Most candidates knew the bonding in Fe is metallic but some did not “describe” it or missed the type of attraction, a minor mistake; others referred to nuclei or protons instead of cations/positive ions. In some cases, candidates referred too ionic bonding, probably still thinking of FeS₂ (not reading the question well). Overall, only 30% answered satisfactorily.

Syllabus sections

Structure 1. Models of the particulate nature of matter » Structure 1.3—Electron configurations » Structure 1.3.5—Each orbital has a defined energy state for a given electron configuration and chemical environment, and can hold two electrons of opposite spin. Sublevels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron. Apply the Aufbau principle, Hund’s rule and the Pauli exclusion principle to deduce electron configurations for atoms and ions up to Z = 36.

Structure 1. Models of the particulate nature of matter » Structure 1.3—Electron configurations » Structure 1.3.7—Successive ionization energy (IE) data for an element give information about its electron configuration. Deduce the group of an element from its successive ionization data.

Structure 3. Classification of matter » Structure 3.1—The periodic table: Classification of elements » Structure 3.1.6—The oxidation state is a number assigned to an atom to show the number of electrons transferred in forming a bond. It is the charge that atom would have if the compound were composed of ions. Deduce the oxidation states of an atom in an ion or a compound.

Structure 2. Models of bonding and structure » Structure 2.3—The metallic model » Structure 2.3.1—A metallic bond is the electrostatic attraction between a lattice of cations and delocalized electrons. Explain the electrical conductivity, thermal conductivity and malleability of metals.

Question 22M.2.HL.TZ2.5

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