Chemistry (Part-II) (UPSC)

Total Questions: 56

41. Which one of the following is produced during the formation of photochemical smog? [2003]

Correct Answer: (c) Ozone
Solution:Photochemical smog is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown haze above cities. It tends to occur more often in summer, because that is when we have the most sunlight.

Primary pollutants: The two major primary pollutants, nitrogen oxides and VOCs, combine to change in sunlight in a series of chemical reactions, to create what are known as secondary pollutants.

Secondary pollutants: The secondary pollutant that causes the most concern is the ozone that forms at ground level. While ozone is produced naturally in the upper atmosphere, it is a dangerous substance when found at ground level. Many other hazardous substances are also formed, such as peroxyacetyl nitrate (PAN).

42. Which of the following substances are found in the beach sands of many parts of Kerala? [2006]

1. Ilmenite
2. Zirecon
3. Sillimanite
4. Tungsten

Select the correct answer using the codes given below:

Correct Answer: (b) 1, 2 and 3 only
Solution:Ilmenite, Zirecon and Sillimanite are found in kollam district in Kerala but tungsten is not found in the beach sands of Kerala.
  1. Ilmenite (FeO·TiO₂): A titanium ore, primarily used to produce titanium dioxide (pigment for paints, plastics) and titanium metal.
  2. Zircon (ZrSiO₄): A zirconium silicate, used in ceramics, refractories, and as a gemstone (zircon).
  3. Sillimanite (Al₂SiO₅): An aluminum silicate, valued for refractory materials (high-temperature bricks) due to its stability.
  4. Tungsten (W): A dense metal with the highest melting point of all metals, used in light bulb filaments, high-speed steels, and cutting tools.

43. Consider the following: [2010]

1. Oxides of Hydrogen
2. Oxides of Nitrogen
3. Oxides of Sulphur

Which of the above causes/cause acid rain?

Correct Answer: (c) 2 and 3 only
Solution:Acid rain is a rain or any other form of precipitation that is unusually acidic, i.e. elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals, and infrastructure through the process of wet deposition. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxides which react with the water molecules in the atmosphere to produce corresponding sulphuric and nitric acids which falls along with rain droplets on ground.

44. Excessive release of the pollutant carbon monoxide (CO) into the air may produce a condition in which oxygen supply in the human body decreases. What causes this condition? [2010]

Correct Answer: (b) The inhaled CO has much higher affinity for haemoglobin as compared to oxygen.
Solution:Carbon Monoxide pollution occurs primarily from emissions produced by fossil fuel powered engines. The incomplete reaction of air with fuel produces the colourless, odourless and highly toxic gas. The main issue with Carbon Monoxide is its health effects. It is capable of binding to the chemicals in our blood, called haemoglobin. It does so far more effectively than oxygen and also stays bound to the haemoglobin for far longer than oxygen does. The effect is that the blood is starved of oxygen, which then affects the rest of the body.

Carbon monoxide has 210 times greater affinity for haemoglobin than oxygen. A small environmental concentration will thus cause toxic levels of carboxyhemoglobin. The affinity of carbon monoxide for myoglobin is even greater than for haemoglobin. Binding to cardiac myoglobin causes myocardial depression, hypotension and arrhythmias. Cardiac decompensation results in further tissue hypoxia and is ultimately the cause of death.

45. Consider the following: [2011-I]

1. Carbon dioxide
3. Oxides of sulphur
2. Oxides of nitrogen

Which of the above is/are the emission/emissions from coal combustion at thermal power plants ?

Correct Answer: (d) 1, 2 and 3
Solution:By products of power thermal plant operation need to be considered in both the design and operation. Waste heat due to the finite efficiency of the power cycle must be released to the atmosphere, using a cooling tower, or river or lake water as a cooling medium. The gas from combustion of the fossil fuels is discharged to the air; this contains carbon dioxide and water vapour, as well as other substances such as nitrogen, nitrogen oxides, sulphur oxides, and (in the case of coal-fired plants) fly ash, mercury and traces of other metals.

46. What is the role of ultraviolet (UV) radiation in the water purification systems? [2012-I]

1. It inactivates /kills the harmful microorganisms in water.
2. It removes all the undesirable odours from the water.
3. It quickens the sedimentation of solid particles, removes turbidity and improves the clarity of water.

Which of the statements given above is/are correct?

Correct Answer: (a) 1 only
Solution:UV systems destroy 99.99% of harmful microorganisms without adding chemicals or changing your water's taste or odour. UV water purification is usually used with other forms of filtration such as reverse osmosis systems or carbon block filters. Only statement 1 is correct.

47. A team of scientists at Brookhaven National Laboratory including those from India created the heaviest anti-matter (anti-helium nucleus). What is/are the implication/ implications of the creation of anti-matter? [2012-I]

1. It will make mineral prospecting and oil exploration easier and cheaper.
2. It will help probe the possibility of the existence of stars and galaxies made of anti-matter.
3. It will help understand the evolution of the universe.

Select the correct answer using the codes given below :

Correct Answer: (b) 2 and 3 only
Solution:It will help probe the possibility of the existence of stars and galaxies made of anti-mater. It will also help in understanding the evolution of the universe.
• An anti-helium nucleus is the antimatter equivalent of a helium nucleus, composed of two antiprotons and two antineutrons (or sometimes an anti-He-3 nucleus: two antiprotons, one antineutron). It confirms that complex antimatter structures can form, helping to understand why the universe is mostly matter.
Implications:
• Probes the existence of antimatter stars/galaxies.
• Aids in understanding the evolution of the universe.
• Tests fundamental physics models.

48. Acid rain is caused by the pollution of environment by [2013-I]

Correct Answer: (d) nitrous oxide and sulphur dioxide
Solution:Acid rain is caused by a chemical reaction that begins when compounds of sulphur dioxide and nitrogen oxide react with molecules in the atmosphere to produce acids.
Acid Rain
• Acid rain is the formation of precipitation in the form of rain, fog, mist or snow that becomes acidic because of the presence of pollutants in the atmosphere.
• The pollutants responsible for acid rain are sulphur dioxide and nitrogen oxides that combine with water vapour to form sulphuric acid and nitric acid.
• These acids then return to the Earth’s surface through rain, snow, or fog, damaging soil, water, vegetation, and man-made structures.
• While normal rain is slightly acidic (pH around 5.6) due to dissolved carbon dioxide, acid rain has a pH much lower than this, often between 4.0–5.0.
The cycle of acid rain works in the following manner:
• Emission of Pollutants: Fossil fuel burning in industries, vehicles, and power plants releases SO₂ and NO₂ into the atmosphere.
• Chemical Reactions: These gases undergo oxidation and dissolve in water droplets, forming sulphuric and nitric acids.
• Deposition: The acids fall back to Earth in the form of rain, snow, fog, or dust, leading to acid deposition.

49. With reference to 'fly ash' produced by the power plants using coal as fuel, which of the following statements is/are correct? [2015-I]

1. Fly ash can be used in the production of bricks for building construction.
2. Fly ash can be used as a replacement for some of the Portland cement concrete.
3. Fly ash is made up of silicon dioxide and calcium oxide only, and does not contain any toxic elements.

Select the correct answer using the code given below.

Correct Answer: (a) 1 and 2
Solution:Fly ash brick (FAB) is a building material, specifically masonry units, containing class C fly ash and water. All fly ash includes substantial amounts of silicon dioxide (SiO₂) aluminum oxide (Al₂O₃) and calcium oxide (CaO), the main mineral compunds in coal-bearing rock strata. Fly ash can be used as a replacement for some of the Portland cement contents of concrete.

50. Brominated flame retardants are used in many household products like mattresses and upholstery. Why is there some concern about their use? [2014-I]

1. They are highly resistant to degradation in the environment.
2. They are able to accumulate in humans and animals.

Select the correct answer using the code given below.

Correct Answer: (c) Both 1 and 2
Solution:Brominated flame retardants used in many household products are highly resistant to degradation in the environment and they are able to accumulate in humans and animals.

There are five main classes of BFRs, listed here with their common uses:

  • Polybrominated diphenyl ethers (PBDEs) - plastics, textiles, electronic castings, circuitry.
  • Hexabromocyclododecanes (HBCDDs) - thermal insulation in the building industry.
  • Tetrabromobisphenol A (TBBPA) and other phenols - printed circuit boards, thermoplastics (mainly in TVs).
  • Polybrominated biphenyls (PBBs) - consumer appliances, textiles, plastic foams.
  • Other brominated flame retardants.