HCS Exam: MCQ Series Chemistry-II
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HCS Exam: MCQ Series Chemistry-II

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Chemistry Multiple Choice Questions For HCS Exam

Haryana Civil Services Exam 2020

Important 20000 MCQ Series For HCS Exam: CHEMISTRY PART-II

Q1. Laughing gas is

(a) Nitric oxide

(b) Nitrous oxide

(c) Nitrogen trioxide

(d) Nitrogen pentoxide

Explanation: Nitrous oxide, commonly known as laughing gas or nitrous, is a chemical compound, an oxide of nitrogen with the formula N2O. At room temperature, it is a colourless non-flammable gas, with a slight metallic scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen.

Q2. The ozone layer in the upper parts of the atmosphere serves as a protective shield against harmful

(a) solar ultraviolet radiation

(b) solar infrared radiation

(c) CO2 in the air

(d) SO2 in the air

Explanation: The ozone layer is a natural layer of gas in the upper atmosphere that protects humans and other living things from harmful ultraviolet (UV) radiation from the sun.

Q3. Silver halides are used in photographic plates because they are

(a) oxidized in air

(b) soluble in hypo solution

(c) reduced by light

(d) totally colourless

Explanation: The light sensitivity of the silver halides is key to the photographic process. Tiny crystals of all three of these compounds are used in making photographic film. When exposed to light, a chemical reaction darkens the film to produce an image.

Q4. Wax used for making candle is chemically a mixture of

(a) aliphatic hydrocarbons

(b) aromatic hydrocarbons

(c) cyclic hydrocarbons

(d) aliphatic and aromatic hydrocarbons

Explanation: An aliphatic compound is a hydrocarbon compound containing carbon and hydrogen joined together in straight chains, branched trains, or non-aromatic rings. Waxes are a class of chemical compounds that are plastic (malleable) near ambient temperatures.

Q5. The gas involved in Bhopal incident was

(a) Hydrogen sulphide

(b) Nitrogen dioxide

(c) Methyl chloride

(d) Methyl isocyanide

Explanation: 3 leaks of toxic methyl isocyanate gas at a Union Carbide plant in the central Indian city of Bhopal produced history's worst industrial disaster, stunning India and the world. Among the questions, the tragedy raised were how it could have happened and who was responsible.

Q6. Alcohol prepared by the distillation of wood is:  

(a) Propyl alcohol

(b) Methyl alcohol

(c) Ethyl alcohol

(d) Glycerol 

Explanation: Methanol (Methyl Alcohol)  was formerly produced by the destructive distillation of wood. The modern method of preparing methanol is based on the direct combination of carbon monoxide gas and hydrogen in the presence of a catalyst.

Q7. Photo-oxidation process is initiated by

(a) light 

(b) heat

(c) oxygen

(d) catalyst

Explanation: Photo-oxidation is therefore the process of oxidation which is caused by shining light on it. Often, light can be used to cause reactions to happen, such as oxidation. The term “photo” comes from “photon” which is light. The effect is facilitated by radiant energy such as UV or artificial light.

Q8. Ultraviolet radiation striking the earth is due to the depletion of

(a) carbon monoxide

(b) carbon dioxide  

(c) ozone

(d) oxygen

Explanation: Ozone is a powerful oxidant (far more so than dioxygen) and has many industrial and consumer applications related to oxidation. This same high oxidizing potential, however, causes ozone to damage mucus and respiratory tissues in animals, and also tissues in plants, above concentrations of about 100 parts per billion. This makes ozone a potent respiratory hazard and pollutant near ground level. However, the so-called ozone layer (a portion of the stratosphere with a higher concentration of ozone, from two to eight ppm) is beneficial, preventing damaging ultraviolet light from reaching the Earth’s surface to the benefit of both plants and animals. Ozone is formed from dioxygen by the action of ultraviolet light and also atmospheric electrical discharges, and is present in low concentrations throughout the Earth’s atmosphere. In total, ozone makes up only 0.6 parts per million of the atmosphere.

Q9. Major gaseous pollutant of the thermal power station is

(a) HjS

(b) NH3

(c) N02  

(d) S02

Explanation: Sulfur dioxides and Combustion of coal is a major important source for particulate air pollution than oil in thermal power plants. The amount of fly ash and SO2 depend on the sulfur and ash content of the fuel used.

Q10. The process of removing calcium and magnesium from hard water is known as

(a) Sedimentation

(b) Filtration

(c) Flocculation

(d) Water softening

Explanation: Water Softening is the process of removing the dissolved calcium and magnesium salts that cause hardness in water.  Water softening is achieved either by adding chemicals that form insoluble precipitates or by ion exchange.

Q11. The tip of the match-stick contains

(a) potassium chlorate

(b) white phosphorus

(c) red phosphorus

(d) phosphorus trichloride

Explanation: The chemical present in matchstick is potassium chlorate, sulfur, starch, and glue.


Q12. Match the source in Column B with the product of

     Column A                                                 Column B

      Product                                                     Source

(a) Formic acid                                                Lemon

(b) Citric acid                                                  Tamarind

(c) Tartaric acid                                               Ants

    A b  c

(a) 3 2 1

(b) 3 1 2

(c) 2 3 1

(d) 2 1 3

Q13. Commercially, sodium bicarbonate is known as

(a) Washing soda

(b) Baking soda

(c) Bleaching powder

(d) Soda ash 

Explanation: " Baking soda/cooking soda " are the commercial names of sodium bicarbonate.

Q14. An emulsifier is an agent which

(a) stabilizes an emulsion

(b) aids the flocculation of an emulsion

(c) accelerates the dispersion

(d) homogenizes an emulsion

Explanation: An emulsifier or emulsifying agent is a compound or substance that acts as a stabilizer for emulsions, preventing liquids that ordinarily don't mix from separating.

Q15. Mortar is a mixture of water, sand and

(a) Slaked lime

(b) Quicklime

(c) Limestone

(d) Gypsum

Explanation: Mortar is a material used in masonry construction to fill the gaps between the bricks and blocks. Mortar is a mixture of sand, a binder such as cement or Slaked lime, and water and is applied as a paste which then sets hard.

Q16. Which of the following substance is highly plastic?

(a) Quartz

(b) Mica

(c) Granite

(d) Clay 

Explanation: Clays exhibit plasticity when mixed with water in certain proportions. When dry, clay becomes firm and when fired in a kiln, permanent physical and chemical changes occur. These reactions, among other changes, cause the clay to be converted into a ceramic material. Because of these properties, clay is used for making pottery items, both utilitarian and decorative. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, and porcelain. Prehistoric humans discovered the useful properties of clay. Some of the earliest pottery shards recovered are from central Honshu, Japan. Clay tablets were used as the first known writing medium, inscribed with cuneiform script through the use of a blunt reed called a stylus. Purpose-made clay balls were also used as sling ammunition.

Q17. The National Chemical Laboratory (India) is located in

(a) Mumbai

 (b) Bengaluru

(c) Hyderabad

(d) Pune  



CSIR-National Chemical Laboratory, Pune.

Q18. An atomic clock is based on transitions in

(a) Sodium  

(b) Caesium

(c) Magnesium

(d) Aluminium

Explanation: Since the beginning of development in the 1950s, atomic clocks have been based on the hyperfine transitions in hydrogen-1, caesium-133, and rubidium-87. 

Q19. Carbon monoxide is an inflammable gas. Which one of the following is also inflammable?

(a) Helium

(b) Nitrogen

(c) Oxygen

(d) Hydrogen

Explanation: At standard temperature and pressure, hydrogen is a colourless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Naturally occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most elements and is present in the water molecule and in most organic compounds. Hydrogen plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules. Hydrogen gas (dihydrogen or molecular hydrogen) is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion for hydrogen is 286 kJ/mol. Pure hydrogen-oxygen flames emit ultraviolet light and are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine compared to the highly visible plume of a Space Shuttle Solid Rocket Booster.

Q20. Which one of the following metals. Does not react with water to produce Hydrogen?

(a) Potassium

(b) Cadmium

(c) Sodium

(d) Lithium 

Explanation: Cadmium does not react with water to produce Hydrogen 

Q21. Ozone consists of 

(a) Oxygen only

(b) Oxygen and Nitrogen 

(c) Hydrogen and Carbon

(d) Oxygen and Carbon

Explanation: Ozone is a gas made up of three oxygen atoms (O3).

Q22. One of the constituents of tear gas is

(a) Ethane  

(b) Ethanol

(c) Ether

(d) Chloropicrin

Explanation: chloropicrin is a colourless liquid that is insoluble in water, with which it is stable. With a vapor pressure of 24 mm Hg, its volatility is between that of phosgene and mustard gas in persistency, although closer to phosgene because it is related to the compound. Tests have shown that chloropicrin causes humans to shut their eyes involuntarily. Chloropicrin can be absorbed systemically through inhalation, ingestion, and the

skin. It is severely irritating to the lungs, eyes, and skin. Because of these properties, chloropicrin can only be delivered in shell form as a chemical weapon. Chloropicrin, today, is used as a fumigant to control pests found in the soil. Although less common, it can be used as a poison for vertebrates, such as rabbits. Chloropicrin is commonly used in combination with other fumigants, such as methyl bromide and sulfuryl fluoride, for increased potency and as a warning agent.

Q23.  The function of sedimentation tank in sewage treatment is to:

(a) Disinfect the sewage

(b) Remove water content. 

(c) Aerate the sewage

(d) Remove suspended solids 

Explanation:  The Primary Settlement or sedimentation tanks are designed to reduce the velocity of the wastewater flow, allowing heavier organic solids (called raw sludge) to settle. They are the first stage of treatment after the removal of rags and grit in the inlet works.

Q24. The two metal ions that cause hardness to water are:

(a) Calcium, Magnesium

(b) Sodium, Calcium 

(c) Sodium, Potassium

(d) Sodium, Magnesium

Explanation: The two main cations that cause water hardness are calcium (Ca2+) and magnesium (Mg2+). 

Q25. Substance used as an antifreeze in radiators of automobiles is:

(a) Methyl alcohol and H20

(b) Methyl alcohol

(c) Ethyl alcohol

(d) Ethyl alcohol and H2O

Explanation: Methyl alcohol and water are used as an anti-freeze in radiators of automobiles.

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