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Chemicals [ Chemistry] [ Science Set 14] | UPPSC Prelims PYQ of Last 30 Years |Important Objective Question Answer, MCQ and QUIZ

 1.  Which one of the following colors is supplied by Sodium Chromate?

a) Blue

c) Red

c) Green

d) Black

Answer. c) Red;

Sodium chromate is a chemical compound with the formula Na2CrO4. It is a yellow ( Yellow-Red), crystalline solid and is often used in laboratories for various chemical reactions and tests.

2. Select the correct answer using the given code:

        List I                            List II

A. Acetone                        1. Fire retardant

B. Carbon tetra chloride   2. Nail Polish

C. Hydrogen Peroxide     3. Bandage of Wounds

D. Fluid Ammonia           4. Refrigerator


        A    B    C    D

a)    4    3    2    1

b)    3    4    1    2

c)    2    1    3    4

d)    1    3    4    2

Answer. c)    2    1    3    4;

Acetone: Acetone is widely used in various industrial and household applications, such as nail polish remover, and as a solvent in chemical processes.

Carbon tetrachloride (CCl4): Carbon tetrachloride is a colorless, heavy, nonflammable liquid. It was once used as a solvent and in fire extinguishers.

Hydrogen peroxide (H2O2): Hydrogen peroxide is commonly used as a disinfectant, bleaching agent, and in various industrial processes.

Anhydrous ammonia (NH3): Anhydrous ammonia is used as a refrigerant and as a source of nitrogen in fertilizers.

3. Which one of the following is used for manufacturing safety matches?

a) Di phosphorus

b) Black Phosphorus

c) Red Phosphorous

d) Scarlet Phosphorus

Answer. c) Red Phosphorous;

White Phosphorus (Di phosphorus): White phosphorus, often referred to as simply "phosphorus," is a highly reactive and toxic allotrope of phosphorus. It has the ability to spontaneously ignite in air.

Black Phosphorus: Black phosphorus is a more stable allotrope of phosphorus. It has a layered structure similar to graphite, with each layer consisting of stacked phosphorus atoms. It has unique electronic properties and has gained attention in electronics and materials science.

Red Phosphorus: Red phosphorus is another stable allotrope of phosphorus. It has a different atomic arrangement from white phosphorus and is not as reactive. Red phosphorus is commonly used in safety matches, fireworks, and as a flame retardant.

4. When kept in air and darkness, which of the following elements glows spontaneously?

a) Red phosphorus

b) White Phosphorus

c) Scarlet phosphorus

d) Violet phosphorus

Answer. b) White Phosphorus;

White Phosphorus (Di phosphorus): White phosphorus, often referred to as simply "phosphorus," is a highly reactive and toxic allotrope of phosphorus. It has the ability to spontaneously ignite in air.

5. Which one of the following solutions of electrolytes is used in the car battery?

a) Sodium Sulfate

b) Nitric Acid

c) Sulfuric Acid

d) Potassium nitrate

Answer. c) Sulfuric Acid;

Sodium Sulfate (Na2SO4):

It is commonly used in detergents and soaps as a filler and a viscosity regulator.

In the paper industry, it's used in the Kraft process for paper pulping.

Sodium sulfate is also used in some chemical reactions and as a drying agent in laboratories.

Nitric Acid (HNO3):

Nitric acid is a strong mineral acid used in the production of fertilizers, explosives, and various chemicals.

It's used in the etching of metals and as a cleaning agent in the semiconductor industry.

In laboratories, it's employed for various analytical and chemical reactions.

Sulfuric Acid (H2SO4):

Sulfuric acid is one of the most widely used industrial chemicals.

It's used in the manufacture of fertilizers, detergents, and chemicals.

In lead-acid batteries, sulfuric acid serves as the electrolyte.

It's employed in various industrial processes, including ore processing and petroleum refining.

Potassium Nitrate (KNO3):

Potassium nitrate has been historically used in gunpowder and fireworks due to its oxidizing properties.

It's used in the production of fertilizers, particularly those containing potassium and nitrogen.

In the food industry, it's used as a food preservative, especially in cured meats.


6. Aquarazia used by goldsmiths is made by combining the following

a) Nitric acid and sulfuric acid

b) Nitric acid and hydrochloric acid

c) Sulfuric acid and hydrochloric acid

d) Citric acid and benzoic acid

Answer. b) Nitric acid and hydrochloric acid;

Aqua regia is a highly corrosive mixture of concentrated nitric acid (HNO3) and concentrated hydrochloric acid (HCl). It is known for its ability to dissolve gold and other noble metals, which is why it is used by goldsmiths and in various analytical and chemical processes.

Goldsmiths use aqua regia primarily for dissolving and refining gold. When gold is alloyed with other metals or impurities, aqua regia can be used to selectively dissolve the gold, leaving behind the other materials. This process is crucial in the production of high-purity gold used in jewelry and other valuable items.

7. Which of the following preservatives is used for colored juices? ( UPPSC PYQ)

a) Sodium Benzoate

b) Potassium metabisulphite

c) Vinegar

d) Potassium Benzoate

Answer. a) Sodium Benzoate;

Sodium Benzoate and Potassium Benzoate:

Both sodium benzoate (NaC7H5O2) and potassium benzoate (KC7H5O2) are commonly used as preservatives in various food and beverage products. They help inhibit the growth of yeast, mold, and bacteria, extending the shelf life of these products.

It acts as a disinfectant and antioxidant, helping to prevent spoilage and preserve the flavor and color of the wine or beer. It's used for sterilizing equipment and as a wine or beer stabilizer.


Vinegar, typically acetic acid (CH3COOH) in water, is a versatile ingredient used in cooking and food preparation. It's used as a condiment, flavor enhancer, and preservative in various cuisines. It's also a key ingredient in salad dressings, pickling solutions, and marinades.

8. Which one of the following substances is used in photography and also as an antichlor?

a) Chrome red

b) Sodium thiosulphate

c) Hydrogen Peroxide

d) Calomel

Answer. b) Sodium thiosulphate;

Chrome Red: "Chrome Red" typically refers to lead chromate pigments, which are used in paints and coatings due to their vibrant red color. However, lead-based pigments are being phased out due to environmental and health concerns.

Sodium Thiosulfate: Sodium thiosulfate (Na2S2O3) is used in various applications lime as Photography, Water Treatment, and medicine.

Hydrogen Peroxide: Hydrogen peroxide (H2O2) is used in Disinfectant, Bleaching Agent, and  Chemical Synthesis.

Calomel: Calomel, or mercurous chloride (Hg2Cl2), has had historical uses in medicine, such as a laxative, and in dentistry. However, its use has significantly declined due to concerns about mercury toxicity.

9. The chemical used as a fixer in the photography is

a) Sodium thiosulphate

b) Borax

c) Sodium tetrathionate

d) Ammonium Molybdate

Answer. a) Sodium thiosulphate;

10. The hypo solution used in photography is an aqueous solution of

a) Sodium thiosulphate

b) Sodium Tetrathionate

c) Sodium Sulphate

d) Ammonium persulfate

Answer. a) Sodium thiosulphate

11. The useful elements in Photography are 

a) Silver nitrate

b) Silver Bromide

c) Sulfuric acid

d) Citric Acid

Answer. b) Silver Bromide

12. Which of the following is coated on the photographic plate?

a) Silver Oxide

b) Silver bromide

c) Silver Chloride

d) Silver Iodide 

Answer. b) Silver bromide

13. Which one of the following chemicals helps in fruit ripening

a) Ethephon

b) Astrazine

c) Isoproturan

d) Malathion

Answer. a) Ethephon;

Ethylene is a natural plant hormone (phytohormone) that plays a key role in the process of fruit ripening. It's often referred to as the "ripening hormone" because it regulates and accelerates the ripening of many fruits. 

Autocatalytic Effect: Ethylene production by fruit can trigger a positive feedback loop, where the presence of ethylene induces further ethylene production. This autocatalytic effect speeds up the ripening process.

Color Change: Ethylene promotes the synthesis of pigments, such as carotenoids, which are responsible for the change in color of many fruits as they ripen. For example, green bananas turn yellow due to ethylene action.

Softening: Ethylene regulates the enzymes responsible for breaking down starches into sugars and cell wall components like pectin. This leads to the softening of fruit and the development of its characteristic texture.

Aroma and Flavor Development: Ethylene also influences the development of aroma compounds and the conversion of organic acids into sugars, contributing to the sweetening and improvement of flavor in ripe fruits.

14. Which of the following chemicals is used for ripening?

a) Sodium Chloride

b) Calcium Carbide

c) Potassium Chloride

d) None of the above

Answer. b) Calcium Carbide

15. Fruit ripening is promoted by which of the following?

a) Carbon dioxide

b) Sulphur dioxide

c) Nitrogen

d) Ethylene

Answer. d) Ethylene

16. Which one of the following pairs is not correctly matched?

a) Fullerenes -- Fluorinated Organic compounds

b) Dry Ice: Solid Carbon Dioxide

c) Kirotin: a protein known as the outer layer of human skin

d) Mustard gas: toxic fluid used in chemical warfare

Answer. a) Fullerenes -- Fluorinated Organic compounds;

Fullerene: Fullerene is a molecule composed entirely of carbon atoms arranged in a hollow sphere, ellipsoid, or tube. The most well-known fullerene is C60, often called "buckyballs." Fullerene molecules have unique properties and have been studied for various applications, including in nanotechnology, drug delivery, and superconductors.

17. Which one of the following pairs is not correctly matched?

a) Dry Ice: Solid Carbon Dioxide

b) Mustard gas: toxic fluid used in chemical warfare

c) Teflon: Fluorine-containing polymer

d) Fullerene -- Fluorine Containing Organic compounds

Answer. d) Fullerene -- Fluorine Containing Organic compounds

18. Which of the following pairs is not correctly matched?

a) Pyrene: Firefighting

b) Sulfur Dioxide: Acid Rain

c) Freon: Refrigerator

d) Fullerene: Fluorine-containing polymer

Answer. d) Fullerene: Fluorine-containing polymer

19. Which one of the following is also known as " wood spirit"?

a) Methyl alcohol

b) Ethyl alcohol

c) Ethylene alcohol

d) Glycerol

Answer. a) Methyl alcohol;

Methyl Alcohol (Methanol):

Methanol is used as an industrial solvent, antifreeze, and fuel. It's also used in the production of formaldehyde and other chemicals. However, it's highly toxic when ingested or absorbed through the skin and should not be consumed.

Ethyl Alcohol (Ethanol):

Ethanol, commonly known as alcohol, is used in various applications. It's a key component in alcoholic beverages, but it also has industrial uses as a solvent, fuel, and an ingredient in hand sanitizers and disinfectants. It can be consumed in moderation as a recreational beverage, but excessive consumption can be harmful.

Ethylene Glycol (Ethylene Alcohol):

Ethylene glycol is primarily used as an antifreeze and coolant in automotive and HVAC systems. It's also used in de-icing solutions for aircraft and as a heat transfer fluid in some industrial applications. It should not be ingested, as it is toxic.


Glycerol, also known as glycerin, has numerous applications. It's used in the food and pharmaceutical industries as a sweetener, thickener, and humectant. It's also used in cosmetics, skin care products, and as an ingredient in some medical preparations.

20. Which of the following fertilizer release the most acid in the soil?

a) Urea

b) Ammonium Sulfate

c) Ammonium Nitrate

d) Calcium ammonium nitrate

Answer. b) Ammonium Sulfate;

Urea (NH2CONH2):

Urea is a common nitrogen-containing fertilizer. It provides a readily available source of nitrogen to plants and is widely used in agriculture to promote plant growth and increase crop yields.

Urea is used in the production of plastics, resins, and adhesives. It's also found in some cosmetics and personal care products.

Ammonium Sulfate ((NH4)2SO4):

Ammonium sulfate is another nitrogen-containing fertilizer. It provides both nitrogen and sulfur to plants and is particularly useful for crops that require a source of sulfur.

It's used in various industrial processes, including the purification of water, as a flame retardant, and in the manufacture of some chemicals.

Ammonium Nitrate (NH4NO3):

Ammonium nitrate is primarily used as a high-nitrogen fertilizer in agriculture. However, due to its explosive potential, it is also regulated and controlled in many countries to prevent its misuse in the production of explosives.

In certain controlled industrial settings, ammonium nitrate can be used as an explosive material.

Calcium Ammonium Nitrate (CAN):

Calcium ammonium nitrate is a nitrogen and calcium-containing fertilizer. It provides nutrients to plants and is commonly used in agriculture to improve soil fertility.

Like ammonium nitrate, calcium ammonium nitrate can be used in the production of explosives in controlled industrial applications.

21. Urea is

a) A nitrogen-containing organic compound

b) A nitrogen-containing inorganic compound

c) Plant hormones

d) An energy absorbent

Answer. a) A nitrogen-containing organic compound

22. Which of the following chemical fertilizers is relatively more soluble in water at 20 degrees centigrade?

a) Ammonium Sulphate

b) Urea

c) Diammonium Phosphate

d) Ammonium Chloride

Answer. b) Urea

23. The most common fertilizer for foliar spraying is 

a) Sodium nitrate

b) Ammonium Chloride

c) Urea

d) D.A.P

Answer. c) Urea

24. Which one of the following compounds is used to make fireproof clothing?

a) Sodium Sulphate

b) Magnesium Sulphate

c) Ferrous Sulphate

d) Aluminum Sulphate

Answer. d) Aluminum Sulphate;

One of the common compounds used for fireproof clothing is Aluminum Sulphate, which is known for its excellent flame-resistant properties.

25. Which of the following is used as a mosquito repellent?

a) Pyrethrum 

b) Rotennone

c) Ephedrine

d) None of the above

Answer. a) Pyrethrum ;

Various chemicals are used in mosquito repellents to deter mosquitoes and other biting insects. The most common active ingredients in mosquito repellents are DEET, Picaridin, Oil of Lemon Eucalyptus (OLE), IR3535, Permethrin

26. Pyrethrin used in mosquito coil is obtained from

a) A seed plant

b) An insect

c) A bacterium 

d) A fungus

Answer. a) A seed plant;

The natural insecticidal properties of pyrethrin are extracted from the dried flower heads of chrysanthemum plants. Pyrethrin is a botanical insecticide that is effective against a wide range of insects, including mosquitoes, flies, and other pests. It is known for its relatively low toxicity to humans and animals while being highly effective in repelling or killing insects.

27. Which one of the following is used as rat poison

a) Zinc Sulphide

b) Lead Sulphide

c) Calcium Phosphate

d) Zinc Phosphide

Answer. d) Zinc Phosphide

28. Which one of the following chemicals has been in use till now for making artificial clouds?

a) Potassium Nitrate

b) heavy Water

c) Sulfur Iodide

d) Silver Iodide

Answer. d) Silver Iodide;

Artificial clouds, often referred to as "cloud seeding," involve the introduction of various substances into the atmosphere to encourage cloud formation and precipitation. The chemicals or substances used for cloud seeding can vary, but some common ones include:

Silver Iodide (AgI): Silver iodide is one of the most commonly used cloud seeding agents. It is similar in structure to ice crystals and can serve as a nucleus around which ice crystals can form in supercooled water droplets within clouds.

Potassium Iodide (KI): Potassium iodide is occasionally used as an alternative to silver iodide in cloud seeding operations.

Calcium Chloride (CaCl2): Calcium chloride can be used in certain cloud seeding methods to encourage the coalescence of cloud droplets, leading to larger and heavier raindrops that fall as precipitation.

Sodium Chloride (NaCl): Sodium chloride (table salt) has been used in some cloud seeding projects, primarily for stimulating the growth of ice crystals in supercooled clouds.

29. Which of the following chemicals is used in the artificial rain

a) Silver Iodide

b) Potassium Chlorate

c) Calcium carbonate

d) Zinc Iodide

Answer. a) Silver Iodide

30. Which of the following is correctly matched?

a) Silver Iodide: Horn Silver

b) Silver Chloride: Artificial Rain

c) Zinc Phosphide: Rat Poison

d) Zinc Sulphide: Philosopher Wool

Answer. c) Zinc Phosphide: Rat Poison;

Silver Iodide (AgI):

Cloud Seeding: Silver iodide is commonly used in cloud seeding to encourage cloud condensation and precipitation. It serves as a nucleating agent to help ice crystals form in clouds, potentially leading to increased rainfall or snowfall.

Silver Chloride (AgCl):

Silver chloride, along with other silver compounds, has been historically used in photographic emulsions. It reacts with light to create photographic images.

Silver chloride is also used in analytical chemistry, particularly in the precipitation of chloride ions.

Zinc Phosphide (Zn3P2):

Rodenticide: Zinc phosphide is used as a rodenticide, commonly in the form of bait. When ingested by rodents, it releases toxic phosphine gas in their stomachs, causing their death.

Zinc Sulfide (ZnS):

Zinc sulfide is often used in the production of phosphorescent materials, such as glow-in-the-dark paints, glow-in-the-dark toys, and some types of luminous watch dials.

31. Red Ink is prepared from

a) Phenol

b) Aniline

c) Congo red

d) Eosin

Answer. d) Eosin;

Phenol (C6H6O):

Antiseptic: Phenol has antiseptic properties and was historically used as a disinfectant and topical antiseptic.

Chemical Intermediates: It is used as a building block in the synthesis of various chemicals, including plastics, dyes, and pharmaceuticals.

Aniline (C6H5NH2):

Dye Production: Aniline is used in the production of dyes and pigments, including synthetic dyes like azo dyes.

Rubber Processing: It's used in the manufacturing of rubber accelerators and antioxidants.

Congo Red:

Dye: Congo Red is a synthetic diazo dye. It is used as a pH indicator, but it's most famous for its use in staining biological samples, such as amyloid deposits in tissues.


Histology and Microscopy: Eosin is a red or pink fluorescent dye used in histology and microscopy to stain biological samples, including cells and tissues, for better visualization.

Cosmetics: It is sometimes used in cosmetics and personal care products


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