Question 1: Define acid rain and explain how it forms in the atmosphere.

Answer: Acid rain is rain with a pH lower than 5.6, forming when sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) are released into the atmosphere, react with water vapour to form sulphuric and nitric acids.

Question 2: Describe the chemical reaction between sulphur dioxide and water vapour that leads to acid rain.

Answer: Sulphur dioxide reacts with water vapour to form sulphuric acid: SO₂ + H₂O → H₂SO₃, which can further oxidise to form sulphuric acid (H₂SO₄).

Question 1: Calculate the mass of sulphur dioxide (SO₂) required to produce 50 grams of sulphuric acid (H₂SO₄). (Atomic masses: S=32, O=16, H=1)

Answer: Approximately 34.4 grams of SO₂ are needed.

Question 2: If a factory releases 200 kg of nitrogen oxides (NOₓ) annually, estimate the amount of nitric acid (HNO₃) that could be formed, assuming complete reaction. (Atomic masses: N=14, O=16, H=1)

Answer: Approximately 150 kg of HNO₃ can be formed.

Question 1: Describe a simple experimental method to test the pH of rainwater and identify safety precautions.

Answer: Collect rainwater in a clean container, use a pH meter or universal indicator to measure pH, and wear protective gloves and goggles to prevent contact with potentially acidic water.

Question 2: Identify the variables that need to be controlled when comparing the acidity of rainwater samples from different locations.

Answer: Variables include temperature, collection time, container cleanliness, and measurement method.

Question 1: A series of rainwater samples from urban and rural areas show average pH values of 4.3 and 5.2 respectively. Explain what these values suggest about pollution levels in the two areas.

Answer: The lower pH (more acidic) in urban areas indicates higher levels of sulphur dioxide and nitrogen oxides, suggesting greater pollution compared to rural areas.

Question 1: Explain why acid rain is harmful to aquatic life and forests. Include chemical effects in your answer. (6 marks)

Answer: Acid rain lowers the pH of water bodies, making the environment too acidic for many aquatic organisms, disrupting their reproduction and survival. In forests, acid rain damages leaves and soil nutrients, leading to weakened trees and reduced biodiversity. Chemically, acids leach harmful metals from rocks and soil, which can enter food chains and cause toxicity.

Question 1: Describe at least two methods industries can use to reduce sulphur dioxide emissions and thus minimise acid rain formation.

Answer: Industries can install flue gas desulphurisation (scrubbers) to remove SO₂ from exhaust gases and switch to low-sulphur fuels to reduce emissions.

Question 2: Explain how the development of cleaner energy sources can help mitigate acid rain issues.

Answer: Using renewable energy sources like wind and solar reduces the burning of fossil fuels, decreasing SO₂ and NOₓ emissions that cause acid rain.