The question asks for the most important harmful effect of Sulfur Dioxide (SO₂), a major air pollutant. We need to evaluate each option based on the known environmental and health impacts of SO₂.
C) It causes ACID RAIN when oxidised to SO₃ and dissolved in water (SO₃ + H₂O → H₂SO₄), and directly damages respiratory tract, irritates eyes and causes bronchitis. This option accurately describes the two most significant and well-established harmful effects of SO₂: its contribution to acid rain and its direct adverse health impacts on the respiratory system.
The question asks to identify the most harmful particulate pollutants to human health among the given options. This requires understanding the different sizes of particulate matter and their impact on the human respiratory and circulatory systems.
Correct Option: C) Very fine particles (PM₂.₅ — particles less than 2.5 µm diameter) that penetrate deepest into lungs, reaching alveoli and entering the bloodstream.
This option correctly identifies PM₂.₅ as the most harmful due to its small size, which allows it to penetrate deep into the lungs (alveoli) and even enter the bloodstream, causing systemic health effects. This deep penetration and systemic absorption are what make PM₂.₅ particularly dangerous.
The question asks to identify the primary acids responsible for acid rain. We need to recall the main atmospheric pollutants that lead to acid rain and the chemical reactions involved in their conversion to acids in rainwater.
Understand Acid Rain: Acid rain is precipitation (rain, snow, fog, etc.) that is unusually acidic, meaning it possesses elevated levels of hydrogen ions (low pH). It is primarily caused by emissions of sulfur dioxide (\(\text{SO}_2\)) and nitrogen oxides (\(\text{NO}_x\)) into the atmosphere.
Formation of Sulphuric Acid: Sulfur dioxide (\(\text{SO}_2\)) is mainly released from the burning of fossil fuels (coal, oil) in power plants and industrial facilities. In the atmosphere, \(\text{SO}_2\) reacts with oxygen and water to form sulphuric acid (\(\text{H}_2\text{SO}_4\)). The key reactions are:
Formation of Nitric Acid: Nitrogen oxides (\(\text{NO}_x\), primarily \(\text{NO}\) and \(\text{NO}_2\)) are produced from high-temperature combustion processes, such as in vehicle engines and power plants. In the atmosphere, \(\text{NO}_x\) reacts with oxygen and water to form nitric acid (\(\text{HNO}_3\)). A simplified reaction sequence is:
Identify the main acids: From the above, it is clear that sulphuric acid (\(\text{H}_2\text{SO}_4\)) and nitric acid (\(\text{HNO}_3\)) are the primary strong acids contributing to acid rain.
Correct Option: B) Sulphuric acid (H₂SO₄) — from oxidation of SO₂, and Nitric acid (HNO₃) — from oxidation of NOₓ dissolved in rainwater
This option accurately identifies both sulphuric acid and nitric acid as the main contributors to acid rain, along with their precursor pollutants (\(\text{SO}_2\) and \(\text{NO}_x\)) and the general process of their formation (
The question asks about the chemical reaction responsible for the damage to the Taj Mahal due to acid rain. This requires knowledge of the composition of marble (Taj Mahal's primary building material) and how it reacts with common acids found in acid rain.
Correct Option: C) CaCO₃ (marble/limestone) + H₂SO₄ → CaSO₄ + H₂O + CO₂ — the acid converts calcium carbonate to calcium sulphate, which then crumbles and washes away. This option accurately describes the chemical reaction and its consequence.
The question asks about the typical pH of normal rainwater. This requires understanding the natural chemical processes that affect the acidity of atmospheric water.
Correct Option: D) 5.6 — slightly acidic due to dissolved carbon dioxide forming carbonic acid: CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻. This option correctly identifies the pH value and provides the accurate chemical explanation for why normal rainwater is slightly acidic.
The question asks about the harmful effects of acid rain. We need to identify the option that comprehensively lists these effects across various domains like human health, materials, ecosystems, and infrastructure.
B) Damages monuments (marble cancer), acidifies soil (reduced crop yield), acidifies lakes (kills aquatic life), corrodes metals, damages forests (especially conifers) and irritates eyes/skin — This option accurately and comprehensively describes the various harmful effects of acid rain on materials, ecosystems, and human health. It covers damage to historical structures, agricultural land, aquatic environments, infrastructure, and natural forests, as well as direct human health impacts.