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Leaving Cert Chemistry: Rates of reaction

How often Rates of reaction comes up on the Chemistry papers, every year it was asked, and questions to try.

HL Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 10 of the last 10 Ordinary Level papers, most recently in 2026. banker

June 2027 is the first exam on the new Chemistry course. These come from the 2016–2026 papers, so read them as a guide.

Rates of reaction, Higher Level(7 marks)

Quick ones on Rates of reaction.

(a)Effect of raising the temperature on the rate of a reaction?
  1. It decreases the rate
  2. It increases the rate
  3. It has no effect
(b)Catalyst used in the school experiment on the decomposition of hydrogen peroxide?
  1. Sodium chloride
  2. Iron(III) oxide
  3. Manganese dioxide
(c)Why does grinding a solid reactant into a powder speed up a reaction?
  1. It increases the surface area available for collisions
  2. It lowers the activation energy of the reaction
  3. It raises the temperature of the solid as it is ground
Show the answers

(a) It increases the rate

(b) Manganese dioxide

(c) It increases the surface area available for collisions

Your turn: Higher Level questions on Rates of reaction.

Higher Level

Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q9
2025Q3
2024Q3
2023Q4(h), Q11(c)
2022Q3, Q11(c)
2021Q10(b)
2019Q9
2018Q7
2017Q3
2016Q3, Q4(i)

Links open the State Examinations Commission’s paper for that year.

More Rates of reaction questions

Rates of reaction, 2 marks

Definition of the rate of a chemical reaction?

  1. The total amount of product formed by the end of the reaction
  2. The temperature at which a reaction starts to happen
  3. The change in concentration of a reactant or product per unit time
Show the answer

The change in concentration of a reactant or product per unit time

Rate is always a change divided by time, so its units are usually mol l⁻¹ s⁻¹. Rate is fastest at the start and falls as reactants are used up.

Rates of reaction, 2 marks

Definition of activation energy?

  1. The energy stored in the products at the end of a reaction
  2. The minimum energy colliding particles need in order to react
  3. The energy released when the particles of a reaction collide with each other
Show the answer

The minimum energy colliding particles need in order to react

Collisions with less than this energy simply bounce apart. Activation energy is why many exothermic reactions still need a spark to start.

Rates of reaction, 2 marks

What is a catalyst?

  1. A substance that speeds up a reaction without being used up
  2. A substance that increases the final yield of product at equilibrium
  3. A substance that raises the activation energy of the reaction
Show the answer

A substance that speeds up a reaction without being used up

It is chemically unchanged at the end, so a small amount can be used over and over.

Ordinary Level

Asked on 10 of the last 10 Ordinary Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q3
2025Q3
2024Q7
2023Q9
2022Q3
2021Q9
2019Q4(f), Q7
2018Q3, Q4(b)
2017Q9
2016Q3, Q11(b)

Links open the State Examinations Commission’s paper for that year.

More Rates of reaction questions

Rates of reaction, 2 marks

Why can fine flour dust in a mill explode?

  1. The flour acts as a catalyst for burning
  2. The flour gives off chlorine gas when it is ground
  3. Its huge surface area lets it burn extremely fast
Show the answer

Its huge surface area lets it burn extremely fast

Fine particles have a very large surface area in contact with air, so a spark can set off a very fast reaction.

Rates of reaction, 2 marks

Metals used as catalysts in a car's catalytic converter?

  1. Lead and mercury
  2. Platinum and rhodium
  3. Iron and copper
Show the answer

Platinum and rhodium

They convert carbon monoxide and nitrogen oxides into carbon dioxide and nitrogen. Lead in petrol poisons these catalysts.

Rates of reaction, 2 marks

On a graph of gas volume against time, where is the rate fastest?

  1. At the start, where the slope is steepest
  2. At the end, where the curve is flat
  3. It is the same all the way
Show the answer

At the start, where the slope is steepest

The reactants are most concentrated at the start. The curve levels off when the reaction is over.

Other Chemistry topics

All of Leaving Cert Chemistry