Chemistry: Environmental Chemistry: UPSC Previous Year Questions (Science and Technology)

Explanation

Acid rain occurs when certain pollutants in the atmosphere react with water vapor to form acids, which then fall to the ground as rain, snow, or fog. The pollutants responsible for acid rain are primarily oxides of nitrogen and oxides of sulfur.

Option 1 is incorrect: Hydrogen itself does not form acidic oxides under typical environmental conditions. The concept of oxides of hydrogen is not commonly associated with acid rain.

Option 2 is correct: Nitrogen oxides, such as nitrogen dioxide, combine with water vapor in the atmosphere to form nitric acid, which contributes to acid rain.

Option 3 is correct: Sulfur oxides, such as sulfur dioxide, react with water vapor to form sulfuric acid, which is another major contributor to acid rain.

Explanation

When carbon monoxide (CO) is inhaled, it binds to hemoglobin in red blood cells with a much stronger affinity than oxygen. Hemoglobin normally binds to oxygen to transport it throughout the body, but CO binds more tightly, forming carboxyhemoglobin. This reduces the ability of hemoglobin to carry oxygen effectively, leading to a decrease in oxygen supply to vital organs and tissues. Carbon monoxide (CO) has approximately 200-250 times more affinity for hemoglobin than oxygen, which means it competes with oxygen for binding sites on hemoglobin.

Explanation

Beach sand minerals are naturally occurring mineral particles found on coastal beaches, often derived from the erosion of rocks and shells. The primary components of beach sand include quartz, a durable and abundant mineral, along with other minerals like feldspar, mica, and ilmenite, as well as heavier minerals such as zircon, rutile, and monazite. The beach sands of many parts of Kerala are known to contain a variety of heavy minerals.

Option 1 is correct: Ilmenite is one of the most abundant minerals in the beach sands of Kerala. It is a source of titanium dioxide, which is used in various industrial applications, including the manufacture of paints and pigments. Odisha is the leading producer of ilmenite, contributing nearly 69% of the total production followed by Kerala and Tamil Nadu.

Option 2 is correct: Zircon is another important mineral found in Kerala’s beach sands. It is used in the production of refractory materials and as a gemstone. Zircon occurs in close association with other heavy minerals such as ilmenite, rutile and monazite in beach sands, along the coastal tracts of the country. Its concentration in the deposits is about 0.6-18.7% of the total heavy minerals. It is found in parts of Gujarat, Maharashtra, Karnataka, Andhra Pradesh, Tamil Nadu, Kerala, Odisha and West Bengal.

Option 3 is correct: Sillimanite is also found in significant amounts in the beach sands. It is an important source of alumina used in the production of aluminum. The resources are located mainly in Odisha, Tamil Nadu, Uttar Pradesh, Andhra Pradesh, Kerala and Assam.

Option 4 is incorrect: Tungsten is not found in the beach sands of Kerala. While it is a valuable mineral, it is not typically associated with the sands in this region. Resources of tungsten-bearing minerals are mainly distributed in Karnataka, Rajasthan, Andhra Pradesh and Maharashtra.

Explanation

Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants like nitrogen oxides and volatile organic compounds (VOCs), including hydrocarbons. The reaction leads to the formation of ozone, which is a key component of photochemical smog. Key Components of Photochemical Smog are:

Nitrogen Oxides - Released from vehicles, industrial emissions, and power plants. They react with sunlight to form ozone. Hydrocarbons: Organic compounds that also contribute to ozone formation when exposed to sunlight. Ozone: The primary harmful product of photochemical smog, which can cause respiratory problems and damage to vegetation. Methane is a potent greenhouse gas, but it does not directly form photochemical smog. While it can contribute indirectly to smog formation by reacting with other pollutants, it is not a primary component like ozone, hydrocarbons, or nitrogen oxides.

Explanation

Water pollution in rivers is primarily measured by the Dissolved Oxygen (DO) level, which indicates the amount of oxygen available for aquatic organisms. A low DO level signifies high pollution, as pollutants like organic waste decompose and consume oxygen, making the water uninhabitable for aquatic life. BOD (Biochemical Oxygen Demand) is the amount of oxygen required by microorganisms to decompose organic matter in water over a specific period (usually 5 days at 20°C). High BOD indicates organic pollution, such as from sewage or agricultural runoff, while low BOD signifies cleaner water. COD (Chemical Oxygen Demand) is the total amount of oxygen required to chemically oxidize both organic and inorganic matter in water. COD provides a broader measure of pollution than BOD, including oxygen demand from inorganic substances.

Explanation

The physico-chemical characteristics of water in water sources are primarily affected by effluents discharged from various sources, including industries, sewage, and agricultural runoff. Effluents introduce pollutants like organic matter, chemicals, heavy metals, and nutrients into water bodies, leading to significant changes in water quality. How Effluents cause Changes:

Chemical Changes: Effluents can alter the pH, increase the concentration of harmful chemicals, and introduce toxic substances. Nutrient Loading: Excessive nutrients (like nitrates and phosphates) from effluents can cause eutrophication, leading to algal blooms. Dissolved Oxygen Levels: Organic pollutants increase the Biological Oxygen Demand (BOD), reducing dissolved oxygen levels and harming aquatic life. Turbidity and Color: Effluents can increase turbidity, reduce light penetration, and alter the color of the water.