Chemistry (Part-V) (Railway)

Total Questions: 50

41. Consider the below statements and identify the correct answer. [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-II)]

Statement I:

Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules.

Statement II:

This property is called catenation.

(1) Statement II is correct, and Statement I is incorrect.
(2) Both the statements are Incorrect.
(3) Statement I is correct, and Statement II is Incorrect.
(4) Both the statements are correct.

Correct Answer: (4) Both the statements are correct.

Solution:Carbon contains four electrons in its outer shell.

• Hence, it has unique property due to which it forms covalent bonds with other carbon atoms.

• This property is called "catenation or self- linking".

42. Bhupesh suffered crop failure for few years. When he got the pH of the soil examined, it was about 11.6. Which of the following compounds can he use to treat the soil of his agricultural field? [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-II)]

(1) Zn(OH)₂
(2) NaCl
(3) Ca(OH)₂
(4) Al₂(SO₄)₃

Correct Answer: (4) Al₂(SO₄)₃

Solution:A pH of 11.6 means that the soil is alkaline.

• Aluminium sulphate (Al₂(SO₄)₃) can be used to treat alkaline soil.

• It is extremely acidic, so it is added to very alkaline soils to balance the pH for plants.

43. During neutralisation reaction H⁺ ion comes from and OH⁻ ion comes from, respectively, to form a water molecule. [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) acid; salts
(2) base; acid
(3) acid; base
(4) salts; base

Correct Answer: (3) acid; base

Solution:Neutralisation is the reaction of an acid and a base. which forms water and a salt.

An acid is a substance or compound that releases hydrogen ions (H⁺) when in solution. A base is a substance that releases hydroxyl ions (OH⁻) when in solution.

The reaction of these two ions to give the neutral molecule water (H⁺ + OH⁻ → H₂O)

44. Which of the following is an example of a thermal decomposition reaction ? [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) 2H₂O → 2H₂ + O₂
(2) 2NaCl (molten) → 2Na + Cl₂
(3) ZnCO₃ → ZnO + CO₂
(4) 2AgCl → 2Ag + Cl₂

Correct Answer: (3) ZnCO₃ → ZnO + CO₂

Solution:A thermal decomposition reaction happens when one reactant gets broken down by heating.

• When zinc carbonate is heated, it will decompose to produce zinc oxide, which is the metal oxide, and carbon dioxide gas. ZnCO₃ → ZnO + CO₂

• From this equation it is visible that the ZnCO₃ is breaking into two smaller molecules which are ZnO and CO₂.

Hence the reaction is a thermal decomposition reaction.

45. Consider the below statements and identify the correct answer. [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

Statement-I: Sodium hydroxide is prepared by chlor-alkali process.

Statement II: Sodium hydroxide is used for making artificial textile fibres (such as rayon).

(1) Statement-I is true, and Statement-II is false.
(2) Both the statements are false.
(3) Statement-II is true, and Statement-I is false.
(4) Both the statements are true.

Correct Answer: (4) Both the statements are true.

Solution:Chlor-alkali process is the one in which an electricity is passed through an aqueous solution of Sodium chloride or brine (NaCl) which decomposes to form sodium hydroxide (NaOH).

• 2NaCl(aq)+2H₂O(l)→ 2NaOH(aq)+Cl₂(g)+H₂(g)

• Sodium hydroxide is used for making artificial textile fibers. It is also used in the manufacture of paper.

46. Consider the below statements and identify the correct answer. [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

Statement I: Series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series.

Statement II: As the molecular mass increases in any homologous series, a gradation in physical properties is seen.

(1) Both the statements are incorrect.
(2) Both the statements are correct.
(3) Statement Il is correct, and Statement I is incorrect.
(4) Statement I is correct, and Statement II is incorrect.

Correct Answer: (2) Both the statements are correct.

Solution:Homologous series is defined as a series of compounds in which the same functional group substitutes for hydrogen in a carbon chain.

• This series will be differing with a successive member of CH₂.

• As the molecular mass increases in any homologous series, a gradation in physical properties is seen. This is because the melting points and boiling points increase with increasing molecular mass.

47. The term (aq) written after the symbol/formula of a substance in a chemical equation indicates that it is present in: [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) gaseous state
(2) solid state
(3) liquid state
(4) a solution in water

Correct Answer: (4) a solution in water

Solution:In a chemical equation, the subscript (aq) after a molecule means that it is aqueous.

• An aqueous solution is a solution in which the solvent is water.

• For example:

Na(s)+H₂O(l)→H₂(g)+NaOH(aq).

This shows that NaOH formed is dissolved in water.

48. The elements which have 2 electrons in their outermost cell are generally: [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) non-metals
(2) metalloids
(3) noble gases
(4) metals

Correct Answer: (4) metals

Solution:The elements which have two electrons in the outermost orbit are called alkaline earth. metals.
• Alkaline metals make up the group 2 of the modern periodic table.
• For example, Magnesium, Calcium, and Strontium have two electrons in their outermost orbit.

49. Seema squeezed a lemon and collected the juice in a glass. She realised that its sourness reduced when she added some water to it. What is the effect of addition of water on the concentration of hydroxide ions? [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) It remains constant
(2) It increases
(3) It reduces
(4) It first increases and then decreases

Correct Answer: (3) It reduces

Solution:In pure water, the concentrations of the hydronium ion (H₂O⁺) and the hydroxide ion (OH⁻) are equal, and the solution is therefore neutral.

• Because of its highly polar structure, liquid water can act as either an acid (by donating a proton to a base) or a base (by using a lone pair of electrons to accept a proton).

• So, adding water to hydroxide ion increases its concentration.

50. Predict the reactants for neutralization reaction where the products are lithium sulphate and water. [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(1) Sulphuric acid and lithium hydroxide
(2) Hydrochloric acid and lithium nitrate
(3) Sulphuric acid and lithium carbonate
(4) Hydrochloric acid and lithium carbonate

Correct Answer: (1) Sulphuric acid and lithium hydroxide

Solution:Sulphuric acid and lithium hydroxide neutralise each other and produce lithium sulfate and water.

• H₂SO₄(aq) + 2LIOH(aq) → Li₂SO₄(aq) + 2H₂O(aq)

• This reaction is a type of double replacement (double displacement) reaction that is also a neutralizsation reaction.

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