DP Chemistry (first assessment 2025)

Question 21M.2.SL.TZ1.3

Date	May 2021	Marks available	[Maximum mark: 7]	Reference code	21M.2.SL.TZ1.3
Level	SL	Paper	2	Time zone	TZ1
Command term	Deduce, Determine, State, Write	Question number	3	Adapted from	N/A

[Maximum mark: 7]

21M.2.SL.TZ1.3

Magnetite, Fe₃O₄, is another ore of iron that contains both Fe²⁺ and Fe³⁺.

Iron exists as several isotopes.

In acidic solution, hydrogen peroxide, H₂O₂, will oxidize Fe²⁺.

Fe²⁺ (aq) → Fe³⁺ (aq) + e⁻

(a)

Deduce the ratio of Fe²⁺:Fe³⁺ in Fe₃O₄.

[1]

Markscheme

1:2 ✔

Accept 2 Fe³⁺: 1 Fe²⁺
Do not accept 2:1 only

(b(i))

State the type of spectroscopy that could be used to determine their relative abundances.

[1]

Markscheme

mass «spectroscopy»/MS ✔

(b(ii))

State the number of protons, neutrons and electrons in each species.

[2]

Markscheme

Award [1 max] for 4 correct values.

(c)

Iron has a relatively small specific heat capacity; the temperature of a 50 g sample rises by 44.4°C when it absorbs 1 kJ of heat energy.

Determine the specific heat capacity of iron, in J g⁻¹K⁻¹. Use section 1 of the data booklet.

[1]

Markscheme

specific heat capacity « = $\frac{q}{m \times ∆ T} / \frac{1000 J}{50 g \times 44 K}$ » = 0.45 «J g⁻¹K⁻¹» ✔

(d(i))

Write the half-equation for the reduction of hydrogen peroxide to water in acidic solution.

[1]

Markscheme

H₂O₂(aq) + 2H⁺(aq) + 2e⁻→ 2H₂O(l) ✔

(d(ii))

Deduce a balanced equation for the oxidation of Fe2+ by acidified hydrogen peroxide.

[1]

Markscheme

H₂O₂(aq) + 2H⁺(aq) + 2Fe²⁺(aq) → 2H₂O(l) + 2Fe³⁺(aq) ✔

Syllabus sections

Structure 1. Models of the particulate nature of matter » Structure 1.4—Counting particles by mass: The mole » Structure 1.4.4—The empirical formula of a compound gives the simplest ratio of atoms of each element present in that compound. The molecular formula gives the actual number of atoms of each element present in a molecule. Interconvert the percentage composition by mass and the empirical formula. Determine the molecular formula of a compound from its empirical formula and molar mass.

Structure 1. Models of the particulate nature of matter » Structure 1.2—The nuclear atom » Structure 1.2.3—Mass spectra. Mass spectra are used to determine the relative atomic masses of elements from their isotopic composition. Interpret mass spectra in terms of identity and relative abundance of isotopes.

Structure 1. Models of the particulate nature of matter » Structure 1.2—The nuclear atom » Structure 1.2.1 - Atoms and negatively charged electrons. Atoms contain a positively charged, dense nucleus composed of protons and neutrons (nucleons). Negatively charged electrons occupy the space outside the nucleus. Use the nuclear symbol ZXA to deduce the number of protons, neutrons and electrons in atoms and ions.

Reactivity 1. What drives chemical reactions? » Reactivity 1.1—Measuring enthalpy changes » Reactivity 1.1.4—The standard enthalpy change for a chemical reaction, ΔH⦵, refers to the heat transferred at constant pressure under standard conditions and states. It can be determined from the change in temperature of a pure substance. Apply the equations Q = mcΔT and ΔH = − Qn in the calculation of the enthalpy change of a reaction.

Tools » Tool 1: Experimental techniques

Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.2—Electron transfer reactions » Reactivity 3.2.2—Half-equations separate the processes of oxidation and reduction, showing the loss or gain of electrons. Deduce redox half-equations and equations in acidic or neutral solutions.

Question 21M.2.SL.TZ1.3

Select a Test

Syllabus sections

Confirm action