Educerie · IB Diploma · Chemistry

Structure 1 — Topic test

Paper 2 style · 20 marks · 30 minutes

The IB data booklet may be used. Show all working. Give answers to an appropriate number of significant figures, with units.

1. Element X has two isotopes: mass 63, relative abundance 69.2 %, and mass 65, relative abundance 30.8 %.

(a) Define the term isotopes. [1]

(b) Calculate the relative atomic mass of X to three significant figures. [2]

(c) Explain why the two isotopes have identical chemical properties. [2]

2. (a) Write the full electron configuration of the Fe²⁺ ion. [2]

(b) The first four ionisation energies of an element, in kJ mol⁻¹, are 738, 1451, 7733 and 10 540. Deduce the group of this element, explaining your reasoning. [3]

3. 0.240 g of magnesium is added to 50.0 cm³ of 0.500 mol dm⁻³ hydrochloric acid.

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

(a) Calculate the amount, in mol, of magnesium. [1]

(b) Calculate the amount, in mol, of hydrochloric acid. [1]

(c) Deduce the limiting reagent, showing your reasoning. [2]

(d) Calculate the volume, in dm³, of hydrogen produced at 273 K and 1.00 × 10⁵ Pa. [2]

4. (a) State two assumptions of the ideal gas model. [2]

(b) Explain why a real gas deviates from ideal behaviour at low temperature. [2]

Total: 20 marks

Command terms in this test. Question 2(b) says deduce — the reasoning must be on the page, not just the group. Questions 1(c), 4(b) say explain, so a description of the difference will not score. Question 4(a) says state, so no justification is needed.

Educerie · original questions written against the published IB syllabus structure for Chemistry Structure 1, first assessment 2025. All data are our own. Last reviewed 5 September 2026.