SOLVED PAPER 2020 (CDS) (I) (General Studies)

Total Questions: 120

21. Match List I with List II and select the correct answer using the code given below the Lists.

List-I (Name)List-II (Formula)
(A) Bleaching powder1. NaHCO₃
(B) Baking soda2. Na₂CO₃ ⋅ 10H₂O
(C) Washing soda3. Ca(OH)₂
(D) Slaked lime4. CaOCl₂
Code:ABCD
(a)4123
(b)4213
(c)3214
(d)3124
Correct Answer: (a)
Solution:The chemical formula of bleaching powder is Ca(OCl) Cl. It is used for water treatment and as a bleaching agent.
  • Sodium bicarbonate (NaHCO₃) is commonly known as baking soda. It is widely used in baking.
  • Sodium Carbonate (Na₂CO₃ ⋅ 10H₂O) is the inorganic compound which is used as washing soda.
  • Calcium hydroxide (Ca(OH)₂) is a colorless crystal i.e., known as slaked lime. Slaked lime is used as a pH-regulating agent and acid neutraliser in soil and water.

Hence, the correct codes are shown in option (a).

22. The number of water molecules associated with copper sulphate molecule to form crystals is

Correct Answer: (c) 5
Solution:Copper sulphate (CuSO₄ ⋅ 5H₂O) is the inorganic compound in which four water molecules are directly attached to Cu atom while one is present as water of crystallisation.

23. Silver articles become black after sometime when exposed to air because

Correct Answer: (c) silver reacts with sulphur in the air to form a coating of silver sulphide
Solution:When the silver articles react with the hydrogen sulphide gas that is present in the air, a black coating of silver sulphide (Ag₂S) is formed. Silver sulphide are insoluble in all the solvents.

24. If x the temperature of a system in kelvin and y is the temperature of the system in °C, then the correct relation between them is

Correct Answer: (b) x = 273 + y
Solution:Relation among the temperatures measured by Celsius scale and Kelvin scale.
K = 273 + C
where, K and C are the temperature of a system in kelvin and celsius (°C ) respectively.
According to question, K = x and C = y
Hence, x = 273 + y

25. The resistivity ρ of a material may be expressed in units of

Correct Answer: (c) ohm-cm
Solution:

The resistivity ρ of a material may be expressed in units of ohm-cm. Resistivity of a conductor is defined as the resistance of a conductor of unit length and unit area of cross-section.

where, l is the length of the conductor, A is the area of cross-section of the conductor and R is the resistance of the conductor.

26. The electromagnetic waves, which are used for satellite communication, are

Correct Answer: (c) radio waves
Solution:The electromagnetic waves, which are used for satellite communication, are radio waves.

In the space wave propagation, the radiowaves emitted from the transmitter antenna reaches the receiving antenna through space. These radiowaves are called space waves. The space waves are the radiowaves of frequency range from 54 MHz to 4.2 GHz.

The space wave propagation is used for television broadcast microwave link and satellite communication.

27. Which one of the following is the correct sequence of organs that occur in the path of urine flow in human body?

Correct Answer: (a) Kidney, ureter, urinary bladder, urethra
Solution:Urine is formed in the kidneys through the filtration of blood. The urine is then passed through the two separate tubes connected to each kidney, known as ureters which open to the urinary bladder, where urine is stored. During urination, the urine is passed from the urinary bladder through the urethra to the outside of the body.

28. Which of the following endocrine glands is not found in pair in humans?

Correct Answer: (b) Pituitary
Solution:Pituitary is a single gland, which is not found in pair like adrenal gland, testie and overies. It is the smallest endocrine gland but serves very important role in the human endocrine system. It directly or indirectly controls almost all other endocrime glands of the body.

It is also known as master gland. It is reddish grey in colour and is roughly oval in shape and about a size of a pea seed. It is located in a small bony cavity of the brain called sella tursica.

29. Which one of the following cell organelles contains DNA?

Correct Answer: (b) Mitochondrion
Solution:Mitochondrion is a semiautonomous cell organelle. Mitochondria were first observed by Kollikar in 1850. They contain DNA as well as ribosomes and are able to synthesise proteins. According to scientific observation, the new mitochondira are originated by the growth and division of pre-existing mitochondria, which can’t occur without the synthesis of proteins.

30. Who among the following scientists introduced the concept of immunisation to the medical world?

Correct Answer: (a) Edward Jenner
Solution:Edward Jenner (17th May, 1749- 26th January, 1823) was an English physician who invented the smallpox vaccine. Jenner is often called a pioneer of immunisation or father of vaccination as he invented first vaccine and also proposed the concept of immunisation.

Robert Koch investigated the anthrax disease cycle in 1876 and studied the bacteria that cause tuberculosis in 1882 and cholera in 1883. He also formulated Koch's postulates.
Robert Hooke looked at a sliver of cork through a microscope lens and first time discovered cells in 1635.
Carl Linnaeus is known as the ‘Father of Taxonomy’. He proposed binominal nomenclature for uniform and unique identification of organisms.