Leaving Cert Chemistry: the new 2027 exam, the investigation and practice questions

The Leaving Cert Chemistry exam in 2027

The weightings are in the NCCA specification, introduced to schools in September 2025, and the marks and question choice are in the Assessment Arrangements 2027. Chemistry is one of the new subjects, so it doesn't get the extra choice that older subjects have. The State Examinations Commission (SEC) sets and marks both parts and has published sample papers.

The SEC hasn't published 2027 exam dates yet (as of 7 November 2026). In 2026 the written exams ran from 3 to 23 June, with results on Friday 21 August (Department of Education and Youth).

The Chemistry in Practice Investigation

The SEC publishes a brief in term two of fifth year, and the 2027 brief is already out. The specification says the investigation should take up to 20 hours, and you:

1. Research an issue related to the brief, gathering and evaluating information from secondary sources.
2. Experiment: form a hypothesis, plan and carry out a laboratory experiment, collect primary data, analyse it and draw conclusions.
3. Argue: build an evidence-based argument in response to the brief, and submit a report in sixth year in the SEC's format.

Keep an investigative log as you go: the specification expects an honest account of how the work unfolded, including what you would change.

What Leaving Cert Chemistry covers

• The Nature of Science (the unifying strand): how scientific knowledge is built and tested, running through everything.
• Nature of Matter: the kinetic theory, the mole and how atomic models developed.
• Behaviour of Matter: gases and the ideal gas equation, periodic trends, bonding from ionic to covalent, and intermolecular forces.
• Interactions of Matter: energy changes, rates and collision theory, equilibrium, and acid-base and redox reactions.
• Matter in our World: practical and analytical chemistry, including standard solutions and finding unknown concentrations.

Grades run from H1 to H8 and O1 to O8, in 10% bands, and give CAO points from 100 for an H1 (CAO grading scale).

Leaving Cert Chemistry practice questions

We wrote these Higher level questions for this guide. Show every step.

1. The mole

Question: how many molecules are in 9.0 g of water? (M_r = 18, Avogadro's constant 6.022 × 10²³ mol⁻¹.) Answer: moles = 9.0 ÷ 18 = 0.50 mol. Molecules = 0.50 × 6.022 × 10²³ = 3.01 × 10²³. Try the Moles Calculator.

2. The ideal gas equation

Question: find the volume of 0.25 mol of gas at 300 K and 100 kPa. (R = 8.314 J K⁻¹ mol⁻¹.) Answer: V = nRT ÷ p = 0.25 × 8.314 × 300 ÷ 100 000 = 6.24 × 10⁻³ m³, or 6.24 litres. Use pressure in pascals and volume in cubic metres.

3. Bonding

Question: chlorine is more electronegative than hydrogen. What type of bond is in hydrogen chloride? Answer: a polar covalent bond: the electrons are shared, but unequally, so chlorine carries a partial negative charge. Bonds sit on a continuum: a large electronegativity difference gives ionic bonding, none gives a pure covalent bond. Name some bond types in our Chemical Bonding course and press Mark.

4. pH and equilibrium

Question: find the pH of 0.010 mol/L hydrochloric acid, and of 0.0010 mol/L sodium hydroxide. Answer: HCl is a strong acid, so [H⁺] = 0.010 and pH = −log(0.010) = 2. For NaOH, pOH = −log(0.0010) = 3, so pH = 14 − 3 = 11. Check them in the pH Calculator.

Common mistakes

• Leaving the investigation late. It's 40% of the grade: plan the research and experiment early and keep your log up to date.
• Units in gas calculations: kPa and litres must become Pa and m³.
• Calling HCl ionic. Unequal sharing is polar covalent.
• Forgetting pOH when finding the pH of a base.

Use a daily paper as a short timed mock

Our daily papers can only practise part of the written exam, which is itself 60% of your grade: they can't help with the investigation. Atoms, Bonding and Moles covers moles, bonding, energy changes, equilibrium and redox; Organic and Equilibrium covers organic chemistry, acids and transition metals; and Chemistry (Ordinary Level) suits Ordinary level. Some topics, such as NMR, Born Haber cycles, entropy and electrode potentials, go beyond the Leaving Cert specification, so skip those. For when mocks happen, see our Leaving Cert mocks guide.

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