DP Chemistry (first assessment 2025)

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Question 21M.2.SL.TZ1.1

Date	May 2021	Marks available	[Maximum mark: 13]	Reference code	21M.2.SL.TZ1.1
Level	SL	Paper	2	Time zone	TZ1
Command term	Deduce, Describe, Explain, Justify, Outline, State, Suggest, Write	Question number	1	Adapted from	N/A

1.

[Maximum mark: 13]

21M.2.SL.TZ1.1

Iron may be extracted from iron (II) sulfide, FeS.

Iron (II) sulfide, FeS, is ionically bonded.

The first step in the extraction of iron from iron (II) sulfide is to roast it in air to form iron (III) oxide and sulfur dioxide.

(a)

Outline why metals, like iron, can conduct electricity.

[1]

Markscheme

mobile/delocalized «sea of» electrons

(b)

Justify why sulfur is classified as a non-metal by giving two of its chemical properties.

[2]

Markscheme

Any two of:

forms acidic oxides «rather than basic oxides» ✔

forms covalent/bonds compounds «with other non-metals» ✔

forms anions «rather than cations» ✔

behaves as an oxidizing agent «rather than a reducing agent» ✔

Award [1 max] for 2 correct non-chemical properties such as non-conductor, high ionisation energy, high electronegativity, low electron affinity if no marks for chemical properties are awarded.

(c(i))

Describe the bonding in this type of solid.

[2]

Markscheme

electrostatic attraction ✔

between oppositely charged ions/between Fe²⁺ and S²⁻ ✔

(c(ii))

State the full electron configuration of the sulfide ion.

[1]

Markscheme

1s² 2s² 2p⁶ 3s² 3p⁶ ✔

Do not accept “[Ne] 3s² 3p⁶”.

(c(iii))

Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.

[1]

Markscheme

«valence» electrons further from nucleus/extra electron shell/ electrons in third/3s/3p level «not second/2s/2p»✔

Accept 2,8 (for O^2–) and 2,8,8 (for S^2–)

(c(iv))

Suggest why chemists find it convenient to classify bonding into ionic, covalent and metallic.

[1]

Markscheme

allows them to explain the properties of different compounds/substances
OR
enables them to generalise about substances
OR
enables them to make predictions ✔

Accept other valid answers.

(d(i))

Write the equation for this reaction.

[1]

Markscheme

4FeS(s) + 7O₂(g) → 2Fe₂O₃(s) + 4SO₂(g) ✔

Accept any correct ratio.

(d(ii))

Deduce the change in the oxidation state of sulfur.

[1]

Markscheme

+6
OR
−2 to +4 ✔

Accept “6/VI”.
Accept “−II, 4//IV”.
Do not accept 2− to 4+.

(d(iii))

Suggest why this process might raise environmental concerns.

[1]

Markscheme

sulfur dioxide/SO₂ causes acid rain ✔

Accept sulfur dioxide/SO₂/dust causes respiratory problems
Do not accept just “causes respiratory problems” or “causes acid rain”.

(e)

Explain why the addition of small amounts of carbon to iron makes the metal harder.

[2]

Markscheme

disrupts the regular arrangement «of iron atoms/ions»
OR
carbon different size «to iron atoms/ions» ✔

prevents layers/atoms sliding over each other ✔

Syllabus sections

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.

Structure 3. Classification of matter » Structure 3.1—The periodic table: Classification of elements » Structure 3.1.3—Periodicity refers to trends in properties of elements across a period and down a group.

Structure 2. Models of bonding and structure » Structure 2.1—The ionic model » Structure 2.1.1—When metal atoms lose electrons, they form positive ions called cations. When non-metal atoms gain electrons, they form negative ions called anions. Predict the charge of an ion from the electron configuration of the atom.

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 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.1—A covalent bond is formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei. The octet rule refers to the tendency of atoms to gain a valence shell with a total of 8 electrons. Deduce the Lewis formula of molecules and ions for up to four electron pairs on each atom.

Structure 2. Models of bonding and structure » Structure 2.1—The ionic model » Structure 2.1.2—The ionic bond is formed by electrostatic attractions between oppositely charged ions. Deduce the formula and name of an ionic compound from its component ions, including polyatomic ions. Binary ionic compounds are named with the cation first, followed by the anion. The anion adopts the suffix “ide”. Interconvert names and formulas of binary ionic compounds.

Reactivity 2. How much, how fast and how far? » Reactivity 2.1—How much? The amount of chemical change » Reactivity 2.1.1—Chemical equations show the ratio of reactants and products in a reaction. Deduce chemical equations when reactants and products are specified.

Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.2—Electron transfer reactions » Reactivity 3.2.1—Oxidation and reduction can be described in terms of electron transfer, change in oxidation state, oxygen gain/loss or hydrogen loss/gain. Deduce oxidation states of an atom in a compound or an ion. Identify the oxidized and reduced species and the oxidizing and reducing agents in a chemical reaction.

Structure 3. Classification of matter » Structure 3.1—The periodic table: Classification of elements » Structure 3.1.5—Metallic and non-metallic properties show a continuum. This includes the trend from basic metal oxides through amphoteric to acidic non-metal oxides. Deduce equations for the reactions with water of the oxides of group 1 and group 2 metals, carbon and sulfur.

Structure 2. Models of bonding and structure » Structure 2.4—From models to materials » Structure 2.4.3—Alloys are mixtures of a metal and other metals or non-metals. They have enhanced properties. Explain the properties of alloys in terms of non-directional bonding.