Question 1: Define the term 'sulphur dioxide' and state one common source in the environment.

Answer: Sulphur dioxide (SO₂) is a colourless gas with a pungent smell, produced mainly from burning fossil fuels containing sulphur, such as coal or oil.

Question 2: Explain how nitrogen oxides contribute to the formation of acid rain.

Answer: Nitrogen oxides (NO and NO₂) react with water in the atmosphere to produce nitric acid, which falls as acid rain, damaging ecosystems and buildings.

Question 3: What is the main difference between carbon monoxide and carbon dioxide in terms of their effects on humans?

Answer: Carbon monoxide is a toxic gas that prevents oxygen from binding to haemoglobin, causing suffocation. Carbon dioxide is a greenhouse gas that contributes to global warming but is less immediately toxic.

Question 1: Calculate the mass of sulphur dioxide emitted if a power station releases 2.5 x 10⁶ m³ of flue gases containing 150 ppm (parts per million) of SO₂. Assume the molar volume of gases is 24 dm³/mol.

Answer: Approximately 25.5 kg of SO₂

Question 2: A vehicle emits 0.8 grams of nitrogen oxides per km. How much NOₓ is emitted after 1500 km of travel?

Answer: 1200 grams (or 1.2 kg)

Question 1: Design a simple experiment to test the effect of sulphur dioxide on plant growth. Describe the variables and safety precautions involved.

Answer: Students could expose identical plants to different concentrations of SO₂ in controlled environments, with one serving as a control. Variables include SO₂ concentration (independent), plant growth (dependent), and environmental conditions kept constant. Safety precautions involve wearing masks, working in well-ventilated areas, and handling SO₂ with appropriate protective equipment to prevent inhalation or contact.

Question 1: A city reports that in winter, the average concentration of nitrogen oxides increases from 40 µg/m³ to 80 µg/m³. Suggest possible reasons for this increase and discuss its potential environmental impacts.

Answer: The increase could be due to higher traffic emissions during winter, increased use of heating systems, or temperature inversions trapping pollutants. Elevated NOₓ levels contribute to smog formation, acid rain, and respiratory problems in residents.

Question 1: Describe the formation and environmental effects of ground-level ozone. (6 marks)

Answer: Ground-level ozone forms when nitrogen oxides and volatile organic compounds react under sunlight. It is a major component of smog, causing respiratory issues, damaging crops, and reducing visibility.

Question 2: Multiple Choice: Which pollutant is primarily responsible for acid rain?

Answer: Sulphur dioxide

Question 1: Explain how catalytic converters reduce emissions of nitrogen oxides and carbon monoxide in vehicle exhausts. Why are they important for environmental protection?

Answer: Catalytic converters facilitate chemical reactions that convert NOₓ and CO into harmless nitrogen, carbon dioxide, and water. They are vital for reducing air pollution, improving air quality, and complying with environmental regulations.