[solved] Chemistry questions with answers – CDS Exam Last 15 years Solved Questions

CDS Exam Chemistry questions with answers (including explanations) of the Last 15 years | CDS OTA Exam – Chemistry questions with solution | Latest CDS Exam Chemistry questions with answers | Multiple Choice Questions (MCQs) of Chemistry

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CDS Exam Solved Chemistry questions

Physics Questions with Explanation
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1. Match List l with List ll and select the correct answer using the codes given below the Lists.
List l
(Mineral)

A. Limestone
B. Copper
C. Bauxite
D. Manganese
List ll
(Industries in which largely used)

1. Cement
2. Electrical goods
3. Manufacture of aeroplanes
4. Steel

(a) A 3, B 4, C 1, D 2
(b) A 1, B 2, C 3, D 4
(c) A 3, B 2, C 1, D 4
(d) A 1, B 4, C 3, D 2

Answer – (b) A 1, B 2, C 3, D 4
Limestone (CaCO3) is the main raw material used in the manufacture of cement. Copper is a good conductor of electricity hence, it is used in electrical goods. Bauxite is an ore of Aluminium. It is used in the manufacture of airplanes. Manganese is used in the steel industry to form manganese steel.

2. The flavor of apple is mainly due to which one of the following?

(a) Formalin
(b) Benzene
(c) Ethanol
(d) Benzaldehyde

Answer – (c) Ethanol
The flavor of apples is mainly due to the ethanol (C2H5OH).

3. Nail varnish remover generally contains which one of the following?

(a) Vinegar
(b) Benzene
(c) Methyl alcohol
(d) Acetone

Answer – (d) Acetone
Nail varnish remover generally contains acetone (CH3COCH3).

4. In which categories did Marie Curie win her two different Nobel prizes?

(a) Physics and Chemistry
(b) Chemistry and Medicine
(c) Physics and Medicine
(d) Chemistry and Peace

Answer – (a) Physics and Chemistry
Marie Curie wins her two different Noble prizes in two different categories i.e., Physics and Chemistry for the discovery of radium and polonium.

5. ‘Freon’ used as refrigerants is chemically known as ___

(a) chlorinated hydrocarbon
(b) fluorinated hydrocarbon
(c) chlorofluoro hydrocarbon
(d) fluorinated aromatic compound

Answer – (c) chlorofluoro hydrocarbon
Chlorofluoro carbon (CF2Cl2) is also known as freon. It is used as the refrigerant in refrigerators and conditions. It is also used as the propellant in aerosols and foams.

6. German silver is an alloy of

(a) gold and silver
(b) copper and silver
(c) copper, zinc, and silver
(d) copper, zinc, and nickel

Answer – (d) copper, zinc, and nickel
German silver is an alloy of copper (25-50%), zinc (25-35%), and nickel (10-35%). It is used in utensils and resistance wire.

7. The tracking of people by trained dogs is based on the recognization of which of the following compounds in the sweat from feet?

(a) Carboxylic acids
(b) Uric acid
(c) Sugar
(d) Salt

Answer – (a) Carboxylic acids
The tracking of people by trained dogs is based on the recognization of carboxylic acid in the sweat from the feet.

8. What of the following metals are present in hemoglobin and chlorophyll, respectively?

(a) Fe and Mg
(b) Fe and Zn
(c) Mg and Zn
(d) Zn and Al

Answer – (a) Fe and Mg
Iron and Magnesium metals are present in haemoglobin and chlorophyll respectively.

9. Which one of the following is involved in the desalination of seawater?

(a) Reverse osmosis
(b) Simple osmosis
(c) Use of sodium aluminum silicate as zeolite
(d) Use of ion-selective electrodes

Answer – (a) Reverse osmosis
The reverse osmosis method is used to obtain pure water from water containing salt or for desalination of seawater.

10. Which of the following isotopes of carbon is/are used in carbon dating?

(a) 6C12 only
(b) 6C13 only
(c) 6C14 only
(d) 6C12 and 6C14

Answer – (c) 6C14 only
The isotope of carbon 6C14 is used in radio carbon dating.

11. An α-particle consvists of which of the following?

(a) 2 protons and 2 neutrons
(b) 1 proton and 1 electron
(c) 2 protons and 4 neutrons
(d) 1 proton and 1 neutron

Answer – (a) 2 protons and 2 neutrons
An α-particle is identical to helium nuclei. It consists of 2 protons and 2 neutrons and is represented by 2He4.

12. Which one of the following substances is made from natural raw materials?

(a) Rayon
(b) Nylon
(c) Polyester
(d) Polystyrene

Answer – (a) Rayon
Rayon is made from naturally occurring cellulose. Rayon is also called artificial silk.

13. Which one of the following metals is less reactive than hydrogen?

(a) Barium
(b) Copper
(c) Lead
(d) Magnesium

Answer – (b) Copper

In the reactivity series of metals, copper is placed below the hydrogen. Hence, it is less reactive than hydrogen. On the other hand barium, lead and magnesium are placed above the hydrogen hence, these are more reactive than hydrogen.

14. Consider the following statements

1. Nitric acid is used in the production of fertilizers.
2. Sulphuric acid is used in the production of explosives.
Which of the statements given above is/are correct?

(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer – (c) Both 1 and 2
Nitric acid is used in the production of fertilizers. The principal chemical produced from nitric acids is ammonium nitrate, sulphuric acid is used in the production of explosives like TNT, nitroglycerine, gun cotton, etc.

15. What is the purpose of adding baking soda to the dough?

(a) To generate moisture
(b) To give a good flavor
(c) To give good color
(d) To generate carbon dioxide

Answer – (d) To generate carbon dioxide
Baking soda has sodium bicarbonate as the chief constituent. It decomposes on heating giving carbon dioxide. This causes dough, cakes, biscuits, etc. to expand and become light.

16. As which one of the following does carbon occur in its purest form in nature?

(a) Carbon black
(b) Graphite
(c) Diamond
(d) Coal

Answer – (a) Carbon black
Carbon occurs in its purest form of carbon black in nature.

17. What is the Jeweller’s rouge?

(a) Ferric oxide
(b) Ferrous oxide
(c) Ferrous carbonate
(d) Ferric carbonate

Answer – (a) Ferric oxide
A very fine powder of ferric oxide is known as “jeweler’s rouge”, “red rouge”, or simply rouge. It is used to put the final polish on metallic jewelry and lenses and historically as a cosmetic.

18. ‘Misch metal’ is widely used in the manufacture of which of the following?

(a) Material of car brake
(b) Smoke detectors
(c) Cigarette lighters
(d) Emergency lights

Answer – (c) Cigarette lighters
‘Misch metal’ alloyed with iron is used in the cigarette lighters. Misch metal is an alloy of cerium (50%), lanthanum (25%), neodymium ( 18%), praseodymium (5%) and other rare metals.

19. What is the pH value of pure water?

(a) 1
(b) 6
(c) 7
(d) 10

Answer – (c) 7
Pure water is neutral in nature hence, the pH value of pure water is 7.

20. Which one of the following is an element?

(a) Topaz
(b) Diamond
(c) Ruby
(d) Sapphire

Answer – (b) Diamond
Diamond is an element. It is an allotrope of carbon. While ruby, topaz, and sapphire are minerals (i.e., compounds). These are valuable gemstones.

21. Which one of the following substances are used in the manufacture of safety matches?

(a) Red phosphorus
(b) White phosphorus
(c) Phosphorus trioxide (P203)
(d) Black phosphorus

Answer – (a) Red phosphorus
Red phosphorus is mostly used in the manufacture of safety matches.

22. Which one of the following is correct? Butter is

(a) a supercooled oil
(b) an emulsion
(c) a molecular solid
(d) None of these

Answer – (d) None of these
Butter is an example of a colloidal dispersion of a liquid in a solid i.e., gel.

23. Which one of the following is the softest?

(a) Sodium
(b) Aluminum
(c) Iron
(d) Copper

Answer – (a) Sodium
Alkali metals such as lithium, sodium, and potassium are soft metals. These can be easily cut with a knife.

24. Which one of the following properties changes with valency?

(a) Atomic weight
(b) Equivalent weight
(c) Molecular weight
(d) Density

Answer – (b) Equivalent weight
Only equivalent weight changes with valency. Atomic weight, molecular weight, and density does not change with valency.
Equivalent weight of the element = 

25. Which of the following has maximum density?

(a) Chloroform
(b) Water
(c) Benzene
(d) Ice

Answer – (b) Water
Water has the maximum density among these because chloroform, benzene, and ice float on water.

26. Which one of the following is used in the preparation of antiseptic solution?

(a) Potassium nitrate
(b) Iodine
(c) Iodine chloride
(d) Potassium chloride

Answer – (b) Iodine
Iodine is a powerful antiseptic. It is used as a tincture of iodine which is a 2-3% iodine solution in alcohol-water.

27. Which one of the following is not a chemical change?

(a) Burning of coal in air
(b) Fermentation of sugar cane juice
(c) Crystallization of table salt from seawater
(d) Cracking of petroleum

Answer – (c) Crystallization of table salt from seawater
A chemical change is a new substance is formed. During crystallization of table salt from seawater, no new substance is formed hence, it is not a chemical change.

28. Statement l: The addition of water to an aqueous solution of HCI decreases the pH.
Statement ll: The addition of water suppresses the ionization of HCl.

(a) Both the statements are individually true and Statement ll is the correct explanation of Statement I
(b) Both the statements are individually true but Statement ll is not the correct explanation of Statement I
(c) Statement I is true, but Statement ll is false
(d) Statement I is false, but Statement ll is true

Answer – (c) Statement I is true, but Statement ll is false
The addition of water to an aqueous solution of HCI decreases the pH because on dilution the number of H+ ions (from water) increases.
Now since [H+] = 10-pH
∴ As [H+] increases pH decreases.

29. Which one of the following is the secondary source of light in a fluorescent lamp?

(a) Neon gas
(b) Argon gas
(c) Mercury vapor
(d) Fluorescent coating

Answer – (d) Fluorescent coating
The fluorescent coating on the glass is the secondary source of light in a fluorescent lamp.

30. Which one of the following is correct? The setting of plaster of Paris is

(a) dehydration
(b) oxidation with atmospheric oxygen
(c) hydration leading to another hydrate
(d) combination with atmospheric CO2

Answer – (c) hydration leading to another hydrate
The setting of plaster of Paris is the hydration leading to another hydrate i.e., gypsum.

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