Chemistry (Part-II) (UPSC)

Total Questions: 56

1. Which one among the following is called philosopher's wool? [2007]

Correct Answer: (c) Zinc oxide
Solution:Philosopher's wool is a oxide of zinc a white powder used as a pigment, cosmetics, glass, inks and in zinc ointment.
About Zinc:
• It is a silvery blue-grey metal with a relatively low melting and boiling point.
• Both lead & zinc are found to occur together in ore along with other metals like silver and cadmium.
• It is the fourth most widely used metal across the globe, trailing only steel, aluminium and copper. Ingress India has self-sufficiency in respect of zinc.
• In India, Rajasthan is endowed with the largest reserves/resources of lead – zinc ore, followed by Andhra Pradesh (3.03%), Madhya Pradesh (1.98%), Bihar etc.
• Global reservoirs of Zinc: Australia accounts for 27% of world’s zinc reserves, followed by China (18%), Russia & Mexico (9% each), Peru(8%), Kazakhstan(5%), USA(4%), etc.
• The largest consumer of zinc is the Galvanising Industry. Owing to its corrosion resistance in varied types of environment, zinc is used for protecting steel by way of galvanizing.
• Large quantities of zinc are used to produce die-castings, which are important in the automobile, electrical and hardware industries.

2. Which one of the following does not contain silver? [2007]

Correct Answer: (b) German silver
Solution:German silver has a color resembling silver, but is an alloy of primarily copper, nickel and zinc. Chlorargyrite is the mineral form of silver chloride (AgCl). It is also known as horn silver. Proustite is a sulfosalt mineral consisting of silver sulfarsenide, Ag, AsS,, known also as light red silver or ruby silver ore, and an important source of the metal. Silver nitrate is an inorganic compound with chemical formula AgNO,, It was once called lunar caustic because silver was called luna by the ancient alchemists.

3. What are Rubies and Sapphires chemically known as? [2008]

Correct Answer: (b) Aluminium oxide
Solution:Both Ruby and Sapphire are varieties of the mineral corundum, which is composed primarily of aluminium oxide (A1,0,). The difference in color between Ruby and Sapphire is due to trace impurities: The red color in rubies is primarily due to the presence of chromium (Cr³*) ions. Sapphires come in various colors (blue, yellow, green, pink, etc.) due to different trace elements. For example, the blue color in sapphires is typically caused by the presence of iron (Fe") and titanium (Ti) ions.

4. Which one of the following is also called Stranger Gas? [2008]

Correct Answer: (c) Xenon
Solution:

Xenon (stranger gas) is a rare, colourless, odourless, chemically stable, and non-reactive gas found in trace amounts in Earth's atmosphere. It is available in solid, liquid, and gaseous states. Commercially, xenon is obtained as a by-product of the air separation process, where air is fractionally distilled into oxygen and nitrogen. Xenon is a noble gas (inert gas) and therefore they do not react with any other elements. However, xenon can form compounds with fluorine and oxygen.
Applications of Xenon:

  • Mountaineering: It has neuroprotective properties that enhances oxygen delivery, supports acclimatisation, and guards against altitude sickness and hypoxia-related damage.
  • Medical: It acts as a natural anesthetic and, when inhaled with oxygen, stimulates hormone production that increases red blood cell count. It is also used to measure blood flow and image the brain, heart, and lungs.
  • Lighting: Used in high-intensity lighting such as flash lamps, strobe lights, and car headlights because it emits bright white light.
  • Industry: Xenon is used in nuclear energy plants, as filling gas in tubes for televisions and radios, and for etching silicon microprocessors using xenon difluoride.
  • Space Exploration: Used as fuel for ion propulsion systems in satellites and deep-space missions.
  • Toxicity: Xenon compounds are strong oxidizing agents that are highly toxic and explosive.

5. Which one of the following pairs of metals constitutes the lightest metal and the heaviest metal, respectively? [2008]

Correct Answer: (b) Lithium and osmium
Solution:The lightest metal in the periodic table is lithium (Li) with atomic number 3 density 0.53 kg/L. Lithium metal is extremely soft (and highly reactive) and so is unusable for many applications.

Osmium is a hard metallic element which has the greatest density of all known elements. It is twice as heavy as lead, and has a specific gravity of 22.59.

6. Lead, ingested or inhaled, is a health hazard. After the addition of lead to petrol has been banned, what still are the sources of lead poisoning? [2012-1]

1. Smelting units

2. Pens and pencils

3. Paints

4. Hair oils and cosmetics

Correct Answer: (b) 1 and 3 only
Solution:People can become exposed to lead through occupational and environmental sources.

This mainly results from: inhalation of lead particles generated by burning materials containing lead, for example during smelting, recycling, stripping leaded paint and plastic cables containing lead and using leaded aviation fuel; and
ingestion of lead-contaminated dust, water (from leaded pipes) and food (from lead-glazed or lead-soldered containers) and from hand-to-mouth behaviour.

Children's innate curiosity and their age-appropriate hand-to-mouth behaviour result in their mouthing and swallowing lead-containing or lead-coated objects, such as contaminated soil or dust and flakes from decaying lead-containing paint.

7. Photochemical smog is a resultant of the reaction among : [2013-1]

Correct Answer: (a) NO₂, O₃ and peroxyacetyl nitrate in the presence of sunlight
Solution:The burning of fossil fuel can create another atmospheric
pollution problem known as Photochemical Smog. Photochemical smog is a condition that develops when primary pollutants like oxides of nitrogen, Volatile organic compounds created from fossil fuel combustion interact under the influence of sunlight to produce secondary pollutants. The major chemical pollutants in Photochemical smog are NO and NO, VOCs(volatile organic compounds), Ozone(O) and PAN (Peroxyacetyl Nitrate). NO, decreases visibility due to yellowish colour. It also contributes to heart and lung problem. Ozone(O,) contributes to bronchial constriction, coughing and wheezing. PAN causes eye irritation, high toxicity to plants.

8. Whichofthe following is/aretheexample/examplesofchemical change? [2014-1]

1. Crystallization of sodium chloride?

2. Melting of ice

3. Souring of milk

Select the correct answer using the code given below.

Correct Answer: (b) 3 only
Solution:Chemical changes occur when a substance combines with another to form a new substance. Crystallization of sodium chloride is not a chemical as water of crystallization can be lost to get salt again. Similarly melting of ice is reversible. However souring of milk is a chemical change as it is not reversible and a new compound is formed.

9. Steel slag can be the material for which of the following? [2020-1]

1. Construction of base road

2. Improvement of agricultural soil

3. Production of cement

Select the correct answer using the code given below

Correct Answer: (d) 1, 2 and 3
Solution:Steel slag, an unavoidable by-product in iron and steel production. Developed countries like Japan, USA have taken lead in making fertilisers using steel-making slag, says 2018's article in Financial Express So, #2 is correct. Steel Slag is used in road metal and bases, producing portland slag cement. It is also used for soil conditioning Says Handbook of Indian Bureau of mines page 6. So, All #3 statements correct.

10. Which one of the following polymers is widely used for making bullet proof material? [1995]

Correct Answer: (d) Polycarbonates
Solution:Polycarbonates are the polymer widely used in making bullet proof material. Bullet proof glass is made by layering a polycarbonate material between pieces of ordinary glass in a process called lamination.

A bullet fired will pierce the outside layer of the glass, but the layered polycarbonate glass material is able to absorb the bullet's energy and stop it.

Polycarbonate panels are used for covering advertising posters, construction of office buildings for sound proofing and polycarbonate is also used for making bullet proof jackets.