The correct option is (a).
Explanation
Acid rain refers to any form of precipitation with acidic components, such as sulfuric or nitric acid, that fall to the ground from the atmosphere. Normal rain has a pH of about 5.6 due to the presence of dissolved carbon dioxide, but acid rain has a pH lower than this value, often caused by anthropogenic emissions.
Statement-wise Analysis:
- Statement 1 is Correct: Acid rain is primarily caused by the emission of Sulphur Dioxide (SO2) and Nitrogen Oxides (NOx), which react with water molecules in the atmosphere to produce acids. While Carbon Dioxide (CO2) naturally dissolves in rain to form weak carbonic acid (giving natural rain its slightly acidic character), the term "Acid Rain" specifically highlights the enhanced acidity due to pollutants like SO2 and NO2 dissolving in raindrops to form Sulphuric Acid (H2SO4) and Nitric Acid (HNO3).
- Statement 2 is Incorrect: Acid rain mainly contains strong mineral acids, specifically Sulphuric Acid and Nitric Acid. Acetic acid (vinegar), citric acid (citrus fruits), and tartaric acid (grapes/tamarind) are weak organic acids and are not the components responsible for the phenomenon of acid rain.
- Statement 3 is Incorrect: Acid rain is highly detrimental to historical monuments, especially those made of marble or limestone (Calcium Carbonate). The acid reacts with the calcium carbonate to form calcium sulphate (gypsum), which flakes off or dissolves, leading to the corrosion of the structure. This phenomenon is often referred to as "Stone Leprosy" or "Marble Cancer."
Key Takeaway:
Acid rain is caused by the atmospheric reaction of Sulphur Dioxide (SO2) and Nitrogen Oxides (NOx) with water vapor, forming strong acids that damage ecosystems, soil chemistry, and marble structures (e.g., the Taj Mahal).