IB Chemistry HL Structure 3: Classification of matter questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type

Multiple choice Written

Difficulty

Easy Medium Hard

Question 1

Multiple choiceMedium1 mark

In a simulation, bromine water is added separately to aqueous potassium chloride and potassium iodide. Which prediction follows from the Group 17 trend in non-metallic character?

Show answer and explanation

Answer: A. Non-metallic character and halogen reactivity decrease down Group 17. Thus, Cl₂ is more reactive than Br₂, while Br₂ is more reactive than I₂. Bromine cannot displace Cl⁻ but can displace I⁻, forming Br⁻ and I₂.

B: Reversing the reactivity order makes Br₂ appear able to displace Cl⁻ but not I⁻. C: Correctly predicts iodide displacement but wrongly extends it to chloride, whose halogen is more reactive. D: Fails to apply the reactivity comparison to iodide; Br₂ displaces I⁻. Remember: A halogen displaces the halide of a less reactive halogen.

Question 2

Paper 2Hard8 marks

Cobalt(II) occurs in differently coloured complexes. A student records the appearance and wavelength of maximum absorption for two solutions.

Complex in solution	Appearance	Wavelength of maximum absorption / nm
[Co(H₂O)₆]²⁺	pink	535
[CoCl₄]²⁻ in chloride-rich solution	blue	610

(a)

State what happens to an electron when visible light is absorbed by a transition-element complex.

[1]

(b)

Use the colour wheel in the data booklet to identify the colour of light absorbed by each solution.

[2]

(c)

A student argues: “Because the solution looks blue, its complex absorbs higher-frequency light than the pink solution.” Assess this claim quantitatively, using the data.

[5]

Question 3

Paper 2Medium6 marks

Two organic compounds, P and Q, are represented by skeletal formulas in Figure 1.

(a)

State the functional group present in each of P and Q.

[2]

(b)

Determine the molecular formula shared by P and Q.

[1]

(c)

Use Figure 1 and your answer to (b).

(i)

State whether P and Q are saturated or unsaturated.

[1]

(ii)

A student argues that P and Q must belong to the same class of organic compounds because they have the same molecular formula. Explain why this conclusion is not justified.

[2]

Question 4

Paper 2Hard9 marks

A laboratory is checking whether molecular formula alone is sufficient to classify oxygen-containing compounds. Figure 1 shows the structural formulae of four compounds.

(a)

Determine the molecular formula of compound A.

[1]

(b)

Using Figure 1, identify two pairs of successive members of homologous series. For each pair, name the series and state the structural change from the smaller member to the larger member.

[4]

(c)

State the general formula for each series identified in (b), using $n$ for the number of carbon atoms.

[2]

(d)

A technician claims that a molecular formula of $\mathrm{C_3H_8O}$ is sufficient to determine uniquely whether a compound belongs to the alcohol or ether series. Evaluate this claim using Figure 1.

[2]

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