Chemistry (Part-IV) (Railway)

Total Questions: 50

41. What is the need to balance chemical equations? [RRB Group 'D' CBT Exam, 17.08.2022 (Shift-III)]

(1) To indicate the ratio of masses of reactants and products in which these react.
(2) To indicate the ratio of volumes of reactants and products in which these react.
(3) To satisfy the law of conservation of mass
(4) To satisfy the law of constant proportions.

Correct Answer: (3) To satisfy the law of conservation of mass

Solution:Chemical equations are balanced to satisfy the law of conservation of mass.

• This law states that matter can be changed from one form to another, but the total amount of mass remains constant.

• According to this law, the mass of products in a reaction must be equal to the mass of reactants so that the balancing is done, and this law is obeyed.

42. Mendeleev's Periodic Law states that: [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) the properties of elements are the periodic function of their atomic masses
(2) the properties of elements are the periodic function of their atomic numbers
(3) the properties of elements are the periodic function of their colour
(4) the properties of elements are the periodic function of their magnetic properties.

Correct Answer: (1) the properties of elements are the periodic function of their atomic masses

Solution:In 1869, Mendeleev formulated a law, now known as the periodic law.

• According to it, the properties of elements are periodic functions of their atomic masses This means, if the elements are arranged in order of increasing atomic masses, then those with similar properties are repeated at regular intervals.

• On the basis of the periodic law. Mendeleev presented his periodic table.

• Henery Moseley gave a modern periodic table, who based on atomic number.

43. The formation of water from hydrogen and oxygen is an example of _________. [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) Combination reaction
(2) oxidation and reduction
(3) decomposition reaction
(4) displacement reaction

Correct Answer: (1) Combination reaction

Solution:Formation of water from hydrogen and oxygen is a combination reaction because hydrogen and oxygen combine to form a single product (water). The reaction occurs as follows: 2H₂ + O₂ → 2H₂O

44. Which of the following reactions represents symbolic combination reaction? [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) XY→X+Y
(2) A+B→C
(3) AB + CD → AC + BD
(4) PQ+R→PR+Q

Correct Answer: (2) A+B→C

Solution:Combination reoction is a reaction in which A and B combined to give C.

∴ A+B→C

45. Calcium sulphate dihydrate is the chemical name of: [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) washing soda
(2) gypsum
(3) baking powder
(4) plaster of paris

Correct Answer: (2) gypsum

Solution:Calcium sulfate dihydrate is a calcium salt and a hydrate with the chemical formula of CaSO₄.₂H₂O.

• Gypsum is a sulfate mineral composed of calcium sulfate dihydrate.

• It appears as white or nearly white, odorless, crystalline solid.

46. The first and second members, respectively, of the ketone homologous series are: [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) propanone, butanone
(2) methanone, ethanone
(3) ethanone, propanone
(4) butanone, propanone

Correct Answer: (1) propanone, butanone

Solution:The homologous series is the group of organic compounds that differ from each other by a methylene (-CH₂) group. A homologous series of ketones can include propanone, butanone, and 2-pentanone with chemical formulas of CH₃COCH₃, CH₃CH₂COCH₃, and CH₃CH₂CH₂COCH₃, respectively, where each successive compound differs from the previous one by a group.

47. Which of the following is most electropositive element ? [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) Cs
(2) Mg
(3) Ca
(4) Na

Correct Answer: (1) Cs

Solution:An electropositive element is an element with atoms that have a tendency to lose electrons and form positive ions.

• Electropositivity increases down the group and decreases in a period.

• Caesium (Cs) metal is at the last in the group of alkali metals, thus it is the most electropositive element.

48. Caustic soda is generally NOT used in the______. [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) detergent industry
(2) fabric industry
(3) paper and pulp industry
(4) manuacture of ammonia

Correct Answer: (4) manuacture of ammonia

Solution:Sodium hydroxide, also known as caustic soda, is an inorganic compound with the formula NaOH.

It is used in many industries; in the manufacture of pulp and paper, textiles, drinking water, soaps, and detergents, and as a drain cleaner.

49. All the compounds of which of the following sets belongs to the same homologous series? [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-II)]

(1) C₃H₈, C₄H₁₀, C₅H₁₂
(2) C₆H₁₀, C₆H₁₂, C₆H₁₄
(3) C₄H₈, C₅H₈, C₆H₁₀
(4) C₂H₆, C₂H₄, C₂H₂

Correct Answer: (1) C₃H₈, C₄H₁₀, C₅H₁₂

Solution:The homologous series is the group of organic compounds that differ from each other by a methylene (-CH₂) group.

C₃H₈ (propane), C₄H₁₀ (Butane) and C₅H₁₂ (Pentane) belong to the same homologous series (alkane CnH₂n+₂ family).

• They are hydrocarbons with C-C single bond.

50. Match the following: [RRB Group 'D' CBT Exam, 18.08.2022 (Shift-III)]

Substance	pH
i. Lemon juice	a. 14
ii. Gastric juice	b. 1.2
iii. Milk of magnesia	c. 2.2
iv. Sodium hydroxide solution	d. 10

(1) i-c, ii-b, iii-d, iv-a
(2) 1-d, ii-b, iii-c, iv-a
(3) i-c, ii-b, iii-a, iv-d
(4) i-a, ii-b, iii-c, iv-d

Correct Answer: (1) i-c, ii-b, iii-d, iv-a

Solution:The correct matches are as follows:

pH value discovered by Sorenson. It lies between 0 to 14. If pH value is 7 is Neutral, PH value less than 7 is acidic, pH value greater than 7 is alkaline.

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