A friend of yours has seen each of the following items in newspaper articles and would like an explanation: (a) acid rain, (b) greenhouse gas, (c) photochemical smog, (d) ozone depletion. Give a brief explanation of each term and identify one or two of the chemicals associated with each.

Verified step by step guidance

1. Step 1: Acid Rain - Acid rain refers to precipitation that is significantly more acidic than normal, due to the presence of elevated levels of hydrogen ions (low pH). It is primarily caused by the emission of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) into the atmosphere, which react with water vapor to form sulfuric acid (H₂SO₄) and nitric acid (HNO₃). These acids can fall to the ground as rain, snow, or fog, leading to environmental damage.
2. Step 2: Greenhouse Gas - Greenhouse gases are atmospheric gases that trap heat from the sun, preventing it from escaping back into space, thus warming the Earth's surface. The most common greenhouse gases include carbon dioxide (CO₂), methane (CH₄), and water vapor (H₂O). These gases contribute to the greenhouse effect, which is a natural process that warms the Earth's surface, but human activities have increased their concentrations, leading to global warming.
3. Step 3: Photochemical Smog - Photochemical smog is a type of air pollution that is formed when sunlight reacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOₓ) in the atmosphere. This reaction produces a mixture of harmful chemicals, including ozone (O₃) at ground level, which can cause respiratory problems and other health issues. It is commonly associated with urban areas with high traffic emissions.
4. Step 4: Ozone Depletion - Ozone depletion refers to the thinning of the Earth's ozone layer, which is located in the stratosphere and protects life on Earth by absorbing the majority of the sun's harmful ultraviolet (UV) radiation. This depletion is primarily caused by human-made chemicals called chlorofluorocarbons (CFCs) and halons, which release chlorine and bromine atoms when they are broken down by UV light, leading to the destruction of ozone (O₃) molecules.
5. Step 5: Summary - Each of these environmental issues is associated with specific chemicals: acid rain with sulfur dioxide and nitrogen oxides, greenhouse gases with carbon dioxide and methane, photochemical smog with volatile organic compounds and nitrogen oxides, and ozone depletion with chlorofluorocarbons and halons. Understanding these terms and their associated chemicals is crucial for addressing and mitigating their impacts on the environment.