CHEMISTRY (Part-VIII) (Railway)

Total Questions: 50

41. The number of double bonds present in Benzene is ............, [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) Three
(2) Four
(3) Two
(4) Six

Correct Answer: (1) Three

Solution:In benzene (C₆H₆), six carbon atoms form a ring structure and there are three single and three double bonds between the carbon atoms.
• Hence, benzene is taken as an example of a cyclic unsaturated carbon compound.

42. Which of the following acts as the deciding factor in the determination of the valency of an atom? [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) Number of electrons in the outermost shell
(2) Number of electrons in the L shell
(3) Number of electrons in the innermost shell
(4) Number of electrons in the K shell

Correct Answer: (1) Number of electrons in the outermost shell

Solution:Valency is a measure of the combining power of an atom.
• The valency of an element is determined by the number of electrons in its outermost shell.
• The valence electrons take part in any chemical reaction because of the outermost orbit usually contains more energy than electrons present in other orbits.

43. Oxides of which of the following elements CANNOT be reduced by H₂, CO and C? [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) Fe
(2) Ca
(3) Pb
(4) Cu

Correct Answer: (2) Ca

Solution:Oxides of potassium, sodium, lithium, barium, calcium, magnesium, and aluminum cannot be reduced by using carbon, carbon monoxide, and hydrogen.
• These are highly active metals that have high affinity for oxygen.
• These metals are obtained by electrolytic reduction of fused metallic salts (halides or oxides) using inert electrodes.

44. The correct increasing order of metallic character is: [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) Ge < Zn < Cu < As
(2) Ga < Ge < Ca < Sc
(3) Ge < Ga < Sc < Ca
(4) Ge < As < Ga < Ca

Correct Answer: (3) Ge < Ga < Sc < Ca

Solution:Metallic character of the element is the ability to form a positive ion by losing electrons.
• Since the metallic character decreases along a period from left to right, therefore, metallic character increases in the order: Ge < Ga < Ca < K (as all these belong to the same period).
• Since metallic character increases down the group from top to bottom, therefore, Ca is more metallic than Sc.

45. Carbon compounds that are linked by only a single bond are known as ______. [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) both saturated and unsaturated compounds
(2) neither saturated nor unsaturated compounds
(3) saturated compounds
(4) unsaturated compounds

Correct Answer: (3) saturated compounds

Solution:The hydrocarbons containing only single bonds are called saturated hydrocarbons.
• This is because each of the carbon atoms is bonded to the maximum number of atoms possible, i.e., we cannot add any other atom to it without replacing the existing one.
• Therefore, it is said to be saturated (with hydrogen) usually.

46. When iron nails come in contact with copper sulphate solution, their colour changes to ______. [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) brown
(2) red
(3) blue
(4) yellow

Correct Answer: (1) brown

Solution:When iron nails come in contact with copper sulphate solution, it becomes brownish in colour and the blue colour of copper sulphate solution disappears.
• This is because iron displaces copper from copper sulphate solution and forms ferrous sulphate which has a pale green colour.
CuSO₄ + Fe → FeSO₄ + Cu
• Iron is more reactive than copper and hence it can displace copper from its solution.

• Iron nails get covered with a red-brown coating of copper metal.

47. An aqueous solution of sodium chloride is known as? [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) Caustic soda
(2) Lime
(3) Lime stone
(4) Brine

Correct Answer: (4) Brine

Solution:Brine is a high-concentration solution of salt (NaCl) in water (H₂O).
• Natural brines occur underground, in salt lakes, or as seawater and are commercially important sources of common salt and other salts, such as chlorides and sulfates of magnesium and potassium.

48. Which of the following is an example of double displacement reaction? [RRB Group 'D' CBT Exam, 27.09.2022 (Shift-I)]

(1) Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(s)
(2) 2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g)
(3) CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
(4) CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat

Correct Answer: (1) Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(s)

Solution:In double displacement reaction, two compounds react, and the positive ions (cation) and the negative ions (anion) of the two reactants switch places, forming two new compounds or products.
• In Na₂SO₄ (aq) + BaCl₂ (aq) → BaSO₄ (s) + 2NaCl (s), barium chloride (BaCl₂) and sodium sulfate (Na₂SO₄) react to form sodium chloride and barium sulphate.
• A white colour precipitate is formed due to the formation of barium sulphate.

49. What is the best method to dispose of hospital waste? [RRB Group 'D' CBT Exam, 28.09.2022 (Shift-II)]

(1) Sterilise and separate metals from cotton
(2) Bury it in deep trenches
(3) Wash before burning
(4) Segregate and recycle

Correct Answer: (1) Sterilise and separate metals from cotton

Solution:Medical waste is disposed of by first making it safe through a sterilization process.
• Waste that cannot be recycled, like gauze or needles, still needs to be made sanitary and non-hazardous before it can be disposed of.
• This process is usually done by using an autoclave.

50. In a given reaction, which element acts as an ion? [RRB Group 'D' CBT Exam, 28.09.2022 (Shift-II)]

Pb(s) + CuCl₂(aq) → PbCl₂(aq) + Cu(s)

(1) Both Pb and Cu
(2) Only Cu
(3) Only Pb
(4) Only Cl₂

Correct Answer: (4) Only Cl₂

Solution:Pb(s) + CuC₁₂ (aq) → PbCl₂ (aq) + Cu(s) is an example of displacement reaction in which one element is replaced by another element in the compound.
• Pb, being more reactive than Cu, displaces Cu from CuCl₂ to form PbCl₂.
• Here, only Cl₂ acts as an ion.

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