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Leaving Cert Chemistry: Environmental chemistry

How often Environmental chemistry comes up on the Chemistry papers, every year it was asked, and questions to try.

HL Asked on 6 of the last 10 Higher Level papers, most recently in 2025. most years

OL Asked on 2 of the last 10 Ordinary Level papers, most recently in 2021.

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

Environmental chemistry, Higher Level(7 marks)

Quick ones on Environmental chemistry.

(a)What does BOD stand for in water analysis?
  1. Basic oxygen dissolved
  2. Biochemical oxygen demand
  3. Biological oxide density
(b)Problem caused by excess nitrates and phosphates entering a river?
  1. Ozone depletion
  2. Acid rain
  3. Eutrophication
(c)Gas produced by burning coal that is a major cause of acid rain?
  1. Sulfur dioxide
  2. Methane
  3. Carbon monoxide
Show the answers

(a) Biochemical oxygen demand

(b) Eutrophication

(c) Sulfur dioxide

Your turn: Higher Level questions on Environmental chemistry.

Higher Level

Asked on 6 of the last 10 Higher Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q4(i)
2024Q4(e)
2023Not asked
2022Not asked
2021Q11(b)
2019Q1
2018Q4(j)
2017Not asked
2016Q9

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

More Environmental chemistry questions

Environmental chemistry, 2 marks

Greenhouse gases warm the lower atmosphere because they absorb?

  1. Ultraviolet light from the Sun
  2. Visible light from clouds
  3. Infrared radiation from the Earth
Show the answer

Infrared radiation from the Earth

The Earth's surface gives off infrared radiation. CO2, methane and water vapour absorb it and send some back down.

Environmental chemistry, 2 marks

Which process in the carbon cycle removes carbon dioxide from the air?

  1. Combustion
  2. Photosynthesis
  3. Respiration
Show the answer

Photosynthesis

Green plants take in CO2 and turn it into glucose. Respiration, combustion and decay return CO2 to the air.

Environmental chemistry, 2 marks

Which gas makes unpolluted rain slightly acidic, at a pH of about 5.6?

  1. Carbon dioxide
  2. Sulfur dioxide
  3. Nitrogen
Show the answer

Carbon dioxide

CO2 dissolves in rain to form weak carbonic acid. Sulfur dioxide and oxides of nitrogen lower the pH further in acid rain.

Ordinary Level

Asked on 2 of the last 10 Ordinary Level papers, most recently in 2021.

Every paper, year by year

YearWhere it came up
2026Not asked
2025Not asked
2024Not asked
2023Not asked
2022Not asked
2021Q4(j)
2019Not asked
2018Not asked
2017Q10(a)
2016Not asked

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

More Environmental chemistry questions

Environmental chemistry, 2 marks

Main greenhouse gas released by burning fossil fuels?

  1. Oxygen
  2. Nitrogen
  3. Carbon dioxide
Show the answer

Carbon dioxide

Carbon dioxide traps heat in the atmosphere, adding to global warming. Methane is another greenhouse gas.

Environmental chemistry, 2 marks

What is the natural greenhouse effect?

  1. Acid rain falling on forests and lakes, damaging trees and fish
  2. Gases in the atmosphere trapping heat, keeping Earth warm enough for life
  3. Destruction of the ozone layer by CFCs, letting more ultraviolet light reach the ground
Show the answer

Gases in the atmosphere trapping heat, keeping Earth warm enough for life

Without it the average surface temperature would be about -18 degrees Celsius. Extra greenhouse gases from human activity enhance the effect.

Environmental chemistry, 2 marks

Main greenhouse gas produced by the digestion of cattle?

  1. Methane
  2. Oxygen
  3. Nitrogen
Show the answer

Methane

Methane traps far more heat than the same mass of carbon dioxide, so agriculture is a big source of greenhouse gases in Ireland.

Other Chemistry topics

All of Leaving Cert Chemistry