Chemistry (Part-2) (CDS-Solved Paper)

Total Questions: 50

41. Who among the following proposed that atom is indivisible? [Morning Shift-2015 (I)]

Correct Answer: (a) Dalton
Solution:

Modern atomic theory was given by
Dalton that states “All matter is made up of atoms and atoms are indivisible”.
Berzelius is known as father of modern chemistry. He determined the exact elementary constituents of large number of compounds.
Rutherford discovered the nucleus of an atom in 1911. While Avogadro is best known for his hypothesis that equal volumes of different gases contain an equal number of molecules, provided they are at the same temperature and pressure.

42. How many elements are there in the 5th period of modern periodic table? [Morning Shift-2015 (I)]

Correct Answer: (c) 18
Solution:

There are a total of 18 elements in the 5th period of modern periodic table. Trend of number of elements in the modern periodic table:
1st period – 2
2nd period – 8
3rd period – 8
4th period – 18
5th period – 18
6th period – 32
7th period – Incomplete

43. Which one among the following is used in making lead pencils? [Morning Shift-2015 (I)]

Correct Answer: (b) Graphite
Solution:

Graphite is used to make lead pencils. The graphite is an allotropic form of carbon that consists of atoms of carbon that possesses a kind of hybridisation in a way that three strong bonds are forming a equilateral triangle in the same plane and a weaker bond perpendicular to that plane. This allows that carbon arranges in “parallel” sheets that slide on each other giving the graphite a high lubricant performance.

44. Sodium metal should be stored in [Morning Shift-2015 (I)]

Correct Answer: (b) kerosene oil
Solution:

Sodium metal is highly reactive due to high electropositive character. Hence, it is stored in kerosene oil, which provides it an inert atmosphere. When sodium metal come in contact with water, it reacts violently.

45. When hard water is evaporated completely the white solid remains in the container. It may be due to the presence of [Morning Shift-2015 (I)]

1. carbonates of Ca and Mg
2. sulphates of Ca and Mg
3. chlorides of Ca and Mg
Select the correct answer using the codes given below.

Correct Answer: (d) All of these
Solution:

Presence of calcium, magnesium and iron salt in the form of hydrogen carbonate, chloride and sulphate in water makes hard water. When this type of water get evaporated, then these salts remains as a white solid in the container.

46. Which one among the following compounds has same equivalent weight and molecular weight? [Morning Shift-2015 (I)]

Correct Answer: (d) NaCl
Solution:

NaCl has same equivalent and molecular weight, because the valence factor for NaCl is one.
Hence,

47. A metallic plate sticks firmly on the mouth of a water vessel made from another metal. By the way of heating, one can detach the plate from the vessel. This is because heat expands [Morning Shift-2015 (I)]

Correct Answer: (c) the vessel more than the plate
Solution:

Since, vessel expands more than the plate, so one can detach the plate by the way of heating.

48. Bagasse, a by-product of sugar manufacturing industry, is used for the production of [Evening Shift-2014 (II)]

Correct Answer: (b) paper
Solution:

Bagasse is the fibrous matter that remains after sugarcane stacks are crushed to extract their juice. It is used as a biofuel and as a substitute for wood in many tropical and subtropical countries for the production of pulp, paper, board etc.

49. The main constituent of gobar gas or bio gas is [Evening Shift-2014 (II)]

Correct Answer: (b) methane
Solution:

Gobar gas or bio gas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen. It is primarily composed of methane (CH₄),  carbon dioxide (CO₂) and may also have small amounts of hydrogen sulphide (H₂S) , moisture and siloxanes. Hence, option (b) is true.

50. Which of the following is a good lubricant? [Evening Shift-2014 (II)]

Correct Answer: (b) Graphite powder
Solution:

A graphite crystal consists of layers of carbon atoms, in which each carbon atom is joined to three other carbon atoms by strong covalent bonds to form flat hexagonal rings. The various layers of carbon atoms are held together by weak van der Waals’ forces.

Due to these weak forces, these layers can slide over one another. This makes the graphite soft and slippery to touch. Hence, due to the sheet like structure, graphite is a comparatively soft substance.