100+ Free LC Chemistry Practice Questions

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Key Facts: LC Chemistry Exam

3 hours, 300 marks

The Leaving Certificate Chemistry written paper duration and total marks

State Examinations Commission past papers

Higher and Ordinary

Chemistry is offered at two levels, Higher (H1-H8) and Ordinary (O1-O8)

State Examinations Commission grading scale

8-point grades

Results use the eight-point scale where each grade is a percentage band

State Examinations Commission grading scale

EUR 116

2026 Leaving Certificate exam fee for a school-based candidate (covers all subjects)

Citizens Information - Examination fees

Section A and B

The paper has two sections of structured, calculation and extended-response questions

State Examinations Commission past papers

Final exam 2026

The outgoing Chemistry syllabus is examined for the last time in June 2026

NCCA - Chemistry curriculum developments

First examined 2027

The revised Chemistry specification is first examined in 2027

NCCA - Chemistry curriculum developments

100

Free original multiple-choice practice questions in this bank

OpenExamPrep

Leaving Certificate Chemistry is an Irish senior-cycle science subject set by the State Examinations Commission (SEC) and sat at Higher Level (H1-H8) or Ordinary Level (O1-O8). It is examined by one 3-hour written paper worth 300 marks with a Section A and Section B of structured, calculation and extended-response questions, plus mandatory practical experiments. There is no single pass mark; grades are percentage bands. The subject is changing over: the outgoing syllabus has its final exam in June 2026 and a revised specification is first examined in 2027. This free bank gives 100 original single-best-answer questions on the core chemistry common to both, covering atomic structure, bonding, stoichiometry, organic, rates and equilibrium, acids and bases, redox and energetics.

Sample LC Chemistry Practice Questions

Try these sample questions to test your LC Chemistry exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1An atom of an element has 17 protons, 18 neutrons and 17 electrons. What is the mass number of this atom?

A.17

B.18

C.34

D.35

Explanation: Mass number equals the number of protons plus the number of neutrons: 17 + 18 = 35. The number of electrons does not affect the mass number because electrons have negligible mass.

2Which scientist proposed that electrons occupy fixed energy levels around the nucleus, explaining the line emission spectrum of hydrogen?

A.John Dalton

B.J. J. Thomson

C.Niels Bohr

D.Ernest Rutherford

Explanation: Niels Bohr proposed that electrons exist in fixed energy levels (orbits) and that light is emitted when an electron falls from a higher to a lower level. This explained the discrete lines in the hydrogen emission spectrum.

3What is the correct electron configuration of a neutral chlorine atom (atomic number 17)?

A.1s2 2s2 2p6 3s2 3p5

B.1s2 2s2 2p6 3s2 3p6

C.1s2 2s2 2p6 3s2 3p3

D.1s2 2s2 2p5 3s2 3p6

Explanation: Chlorine has 17 electrons filled in order of increasing energy: 1s2 2s2 2p6 3s2 3p5. This gives 2 + 2 + 6 + 2 + 5 = 17 electrons, leaving 3p one electron short of a full subshell.

4Two atoms with the same number of protons but different numbers of neutrons are described as:

A.Allotropes

B.Isomers

C.Isotopes

D.Ions

Explanation: Isotopes are atoms of the same element (same proton number) that have different numbers of neutrons and therefore different mass numbers. Chlorine-35 and chlorine-37 are a common example.

5Chlorine has two isotopes: chlorine-35 (75% abundance) and chlorine-37 (25% abundance). What is its relative atomic mass?

A.35.0

B.35.5

C.36.0

D.37.0

Explanation: Relative atomic mass is the weighted mean: (35 x 0.75) + (37 x 0.25) = 26.25 + 9.25 = 35.5. The more abundant lighter isotope pulls the average closer to 35.

6Moving from left to right across a period in the periodic table, the atomic radius generally:

A.Increases

B.Decreases

C.Stays the same

D.Increases then decreases

Explanation: Across a period the nuclear charge increases while electrons are added to the same main energy level. The greater attraction pulls the electron cloud inward, so atomic radius decreases across a period.

7Which of the following best defines the first ionisation energy of an element?

A.The energy released when an atom gains one electron

B.The energy needed to remove one electron from each atom in a mole of gaseous atoms

C.The energy needed to break one mole of bonds

D.The energy released when one mole of ions is formed in solution

Explanation: First ionisation energy is the energy required to remove one electron from each atom in a mole of gaseous atoms, forming a mole of singly charged positive ions. It is always endothermic.

8Why is the second ionisation energy of any element always greater than its first ionisation energy?

A.The atom becomes larger after losing an electron

B.An electron is removed from a more shielded shell

C.The electron is removed from a positively charged ion, which holds electrons more tightly

D.The nuclear charge decreases after the first electron is removed

Explanation: After the first electron is lost the species is a positive ion with the same nuclear charge but fewer electrons, so each remaining electron is held more tightly. More energy is therefore needed to remove the second electron.

9An element is in Group 2 and Period 3 of the periodic table. What is this element?

A.Beryllium

B.Magnesium

C.Calcium

D.Sodium

Explanation: Period 3 is the third row and Group 2 is the second column (the alkaline earth metals). The element at that position is magnesium, with electron configuration 1s2 2s2 2p6 3s2.

10Which element in Period 3 has the highest electronegativity?

A.Sodium

B.Aluminium

C.Silicon

D.Chlorine

Explanation: Electronegativity increases across a period as nuclear charge rises and atomic radius falls. Of these Period 3 elements chlorine is furthest right (excluding argon), so it has the highest electronegativity.

About the LC Chemistry Exam

Leaving Certificate Chemistry is a senior-cycle science subject in the Irish second-level system, examined by the State Examinations Commission (SEC) at Higher Level or Ordinary Level. It is assessed by a single 3-hour written paper worth 300 marks, divided into Section A and Section B of structured, calculation and extended-response questions, supported by mandatory practical experiments completed during the course. Core content includes atomic theory and the periodic table, chemical bonding and molecular shapes, stoichiometry and volumetric analysis, organic chemistry, rates of reaction and chemical equilibrium, acids and bases, oxidation-reduction, gases and thermochemistry. The subject is in transition: the outgoing syllabus is examined for the last time in June 2026, and a revised specification (introduced for fifth-year students from September 2025) is first examined in 2027. This 100-question bank concentrates on the chemistry common to both, so it stays useful across the changeover.

Assessment

Official paper: a single written examination with Section A and Section B of structured, calculation and extended-response questions (not fixed multiple choice). This bank provides 100 original single-best-answer multiple-choice questions for concept revision.

Time Limit

The official Chemistry written paper is 3 hours and worth 300 marks.

Passing Score

No single pass mark. Results use the eight-point scale: Higher Level H1-H8 and Ordinary Level O1-O8, each a percentage band (H1/O1 90-100%, H2/O2 80 to under 90%, down to H8/O8 0 to under 30%).

Exam Fee

In 2026 the Leaving Certificate examination fee is EUR 116 for a school-based candidate (EUR 301 for a school-going repeat candidate); full medical card holders are exempt. The fee covers all subjects entered, not Chemistry alone. (State Examinations Commission (SEC), Ireland)

LC Chemistry Exam Content Outline

26%

Atomic structure, periodic table and bonding

Atomic models and the development of atomic theory, electron configuration and orbitals, the periodic table and periodic trends in atomic radius, ionisation energy and electronegativity, plus ionic and covalent bonding, VSEPR molecular shapes and intermolecular forces (hydrogen bonding, dipole-dipole and van der Waals forces).

18%

Stoichiometry and volumetric analysis

The mole concept, relative atomic and molecular mass, empirical and molecular formulas, balancing equations, concentration in mol/L and g/L, percentage yield, and quantitative volumetric analysis (acid-base and redox titrations), a major source of Higher Level calculation marks.

18%

Organic chemistry

Alkanes, alkenes and alkynes, functional groups (alcohols, aldehydes, ketones, carboxylic acids, esters and halogenoalkanes), structural isomerism, aromatic chemistry (benzene), and characteristic reactions including substitution, addition, esterification, oxidation and combustion.

24%

Rates, equilibrium, acids and bases

Rates of reaction and the effect of concentration, temperature, surface area and catalysts; dynamic chemical equilibrium and Le Chatelier's principle; pH and the pH scale; strong and weak acids and bases (Bronsted-Lowry and Arrhenius); neutralisation, conjugate pairs and indicators.

14%

Oxidation-reduction and energetics

Oxidation numbers, oxidising and reducing agents, redox half-reactions and electrochemistry; the gas laws and the ideal gas idea; and thermochemistry including exothermic and endothermic reactions, heats of reaction, Hess's law and bond energy.

How to Pass the LC Chemistry Exam

What You Need to Know

Passing score: No single pass mark. Results use the eight-point scale: Higher Level H1-H8 and Ordinary Level O1-O8, each a percentage band (H1/O1 90-100%, H2/O2 80 to under 90%, down to H8/O8 0 to under 30%).
Assessment: Official paper: a single written examination with Section A and Section B of structured, calculation and extended-response questions (not fixed multiple choice). This bank provides 100 original single-best-answer multiple-choice questions for concept revision.
Time limit: The official Chemistry written paper is 3 hours and worth 300 marks.
Exam fee: In 2026 the Leaving Certificate examination fee is EUR 116 for a school-based candidate (EUR 301 for a school-going repeat candidate); full medical card holders are exempt. The fee covers all subjects entered, not Chemistry alone.

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

LC Chemistry Study Tips from Top Performers

1Drill the calculation routines until they are automatic: moles from mass, concentration in mol/L, titration calculations, percentage yield and pH from hydrogen-ion concentration.

2Learn the mandatory experiments thoroughly, including apparatus, the reason for each step, sources of error and the underlying chemistry, because the written paper draws directly on them.

3For organic chemistry, build a reaction map for each functional group so you can predict products of substitution, addition, esterification and oxidation rather than memorising isolated equations.

4Practise past SEC papers against the official marking schemes so you write answers in the exact form and key words the examiners reward.

5For equilibrium and rates, reason from Le Chatelier's principle and collision theory rather than recalling specific examples, so you can handle unfamiliar systems.

6Keep units and significant figures consistent in every calculation; many marks are lost from correct method with the wrong unit or a rounding slip.

Frequently Asked Questions

Is the Leaving Certificate Chemistry exam multiple choice?

No. The official SEC paper is a single 3-hour written paper worth 300 marks with a Section A and Section B of structured, calculation and extended-response questions. These multiple-choice questions are an extra concept-revision aid, not the real format.

How long is the Leaving Cert Chemistry exam and how many marks?

The Chemistry written paper is 3 hours long and worth 300 marks. It is taken at either Higher Level or Ordinary Level on a single exam day during the June Leaving Certificate session.

Is there a pass mark for Leaving Cert Chemistry?

There is no single pass mark. Results use the eight-point grade scale (Higher Level H1-H8, Ordinary Level O1-O8), where each grade is a percentage band, for example H1/O1 is 90-100% and H4/O4 is 60 to under 70%.

What does the Leaving Cert Chemistry course cover?

Core topics include atomic structure and the periodic table, bonding and molecular shapes, stoichiometry and volumetric analysis, organic chemistry, rates and equilibrium, acids and bases, oxidation-reduction, gases and thermochemistry, supported by mandatory practical experiments.

Is the Chemistry syllabus changing?

Yes. The outgoing syllabus is examined for the last time in June 2026. A revised specification, introduced for fifth-year students from September 2025, is first examined in 2027. This bank focuses on the core chemistry common to both so it stays useful across the change.

Are these official SEC practice questions?

No. These are original OpenExamPrep questions modelled on Leaving Certificate Chemistry topics. The State Examinations Commission publishes official past papers, sample papers and marking schemes separately on examinations.ie.