Railway Science (Chemistry-Chemical Reaction) (Part-III)

Total Questions: 50

31. Which of the following is the correct balanced equation for the given chemical reaction? [RRC Group D 19/09/2022 (Afternoon)]

Fe+ 𝐻₂O β†’ F𝑒₃𝑂₄ + 𝐻₂

Correct Answer: (d) 3Fe(s)+ 4𝐻₂O (g) β†’ F𝑒₃𝑂₄ (s) + 4𝐻₂ (g)
Solution:

In the above reaction, water (Hβ‚‚O) acts as an oxidising agent as it oxidises iron (Fe) to form ferric(III) oxide (F𝑒₃𝑂₄) and hydrogen (Hβ‚‚). This is the example of displacement reaction.

32. Precipitation reactions occur when cation of one reactant and anion of second reactant, found in an aqueous solution, combine to form_______. [RRC Group D 19/09/2022 (Evening)]

Correct Answer: (a) an insoluble ionic solid
Solution:

Precipitation reactions - It occurs when cations and anions in aqueous solution combine to form an insoluble ionic solid called a precipitate. Example:- Naβ‚‚SOβ‚„ (aq) + CaClβ‚‚ (aq) β†’ CaSOβ‚„ (s) + 2 NaCl (aq). In this reaction CaSOβ‚„ (Calcium sulfate) is precipitate. Naβ‚‚SOβ‚„ - Sodium sulfate, CaClβ‚‚ - Calcium chloride, NaCl – Sodium chloride.

33. Which of the following gases are evolved at the anode and the cathode, respectively, during electrolytic decomposition of aqueous sodium chloride? [RRC Group D 19/09/2022 (Evening)]

Correct Answer: (d) C𝑙₂ gas at the anode and 𝐻₂ gas at the cathode.
Solution:

Electrolysis of sodium chloride- 2Na⁺(l) + 2Cl⁻(l) β†’ 2Na(l) + Clβ‚‚(g). It is an important process to manufacture many bulk chemicals of commercial utility, like chlorine, sodium hydroxide etc. Electrolysis - It is Process of chemical decomposition by passing an electric current through an ion containing liquid or solution. Electrolysis of water- 2Hβ‚‚O(l) β†’ 2Hβ‚‚(g) + Oβ‚‚(g)

34. What happens when aqueous silver nitrate is added to sodium chloride solution? [RRC Group D 19/09/2022 (Evening)]

Correct Answer: (b) White precipitate of silver chloride is produced.
Solution:

Double displacement reaction - A type of reaction in which two reactants exchange ions to form two new compounds. Double displacement reactions take the form - (AB + CD β†’ AD + CB).
Example - AgNO₃ (aq) (Silver nitrate) + NaCl (aq) (Sodium Chloride) β†’ AgCl (s)(Silver chloride) + NaNO₃ (aq)(Sodium nitrate), BaClβ‚‚(aq) + Naβ‚‚SOβ‚„(aq) β†’ BaSOβ‚„(s) + 2NaCl(aq).

35. Which of the following reactions produces water insoluble salts? [RRC Group D 20/09/2022 (Morning)]

Correct Answer: (c) Precipitation reaction
Solution:

Precipitation reaction - When cations and anions in aqueous solution combine to form an insoluble ionic salt (a precipitate). Example - AgNO₃ (Silver nitrate) + KCl (Potassium Chloride) β†’ AgCl (Silver chloride) + KNO₃ (Potassium Nitrate).

36. Which of the following compounds is prepared when sodium chloride reacts with carbon dioxide in the presence of ammonia and water? [RRC Group D 20/09/2022 (Afternoon)]

Correct Answer: (d) π‘π‘Žπ»πΆπ‘‚β‚ƒ
Solution:

(Sodium bicarbonate, Baking Soda). COβ‚‚ (Carbon dioxide) + Hβ‚‚O (Water) + NH₃ (Ammonia) + NaCl (Sodium Chloride) β†’ NaHCO₃ (Sodium bicarbonate) + NHβ‚„Cl (Ammonium Chloride), 2NaHCO₃ β†’ Naβ‚‚CO₃ + COβ‚‚ + Hβ‚‚O.
Baking Soda : Used as an antacid to treat indigestion and heartburn, used in making baking powder. Naβ‚‚SOβ‚„ - Sodium sulphate.

37. Which of the following is reduced in the given reaction? [RRC Group D 20/09/2022 (Afternoon)]

ZnO+C→ Zn + CO

Correct Answer: (a) ZnO
Solution:

Carbon is oxidized (due to gain of oxygen) and Zinc Oxide is reduced (due to loss of oxygen). Oxidation - Addition of oxygen/electronegative elements to a substance or removal of hydrogen/ electropositive elements from a substance. Reduction - Removal of oxygen/electronegative element from a substance or addition of hydrogen/electropositive element to a substance. Redox reaction - Reaction which involves both oxidation and reduction.

38. Which of the following are produced in a neutralization reaction? [RRC Group D 20/09/2022 (Afternoon)]

Correct Answer: (a) Salt and water
Solution:

Neutralization Reaction - A chemical reaction in which an acid and base quantitatively react together to form a salt and water as products. Precipitation reactions - A chemical reaction occurring in an aqueous solution where two ionic bonds combine, resulting in the formation of an insoluble salt. Example - Naβ‚‚SOβ‚„ (Sodium Sulphate) + BaClβ‚‚ (Barium Chloride) β†’ BaSOβ‚„ (Barium Sulphate) + 2NaCl (Sodium Chloride).

39. MnOβ‚‚ + 4HCl β†’ 𝑀𝑛𝐢𝑙₂ + 2𝐻₂𝑂 + 𝐢𝑙₂ According to the given reaction, which of the following statements is INCORRECT? [RRC Group D 20/09/2022 (Evening)]

Correct Answer: (d) 𝐢𝑙₂ is oxidized to HCl.
Solution:

Redox reaction - A chemical reaction in which electrons are transferred between two reactants participating. Oxidation and reduction both take place together in a single reaction.
Example - MnOβ‚‚ (Manganese dioxide) + 4HCl (Hydro Chloride) β†’ MnClβ‚‚ (Manganese chloride )+ 2Hβ‚‚O (water) + Clβ‚‚ (Chlorine). In the given reaction, HCl loses hydrogen to form Clβ‚‚ . Hence, HCl is oxidised in the given reaction.

40. Select the product formed in a reaction between barium chloride and aluminium sulphate. [RRC Group D 20/09/2022 (Evening)]

Correct Answer: (d) Solid Ba𝑆𝑂₄ is formed.
Solution:

Double displacement reaction - Two chemical substances react by exchanging ions to produce two new molecules. Example - 3BaClβ‚‚ (Barium chloride) + Alβ‚‚(SOβ‚„)₃ (Aluminium sulfate ) β†’ 2AlCl₃ (aluminium chloride) + 3BaSOβ‚„ (Barium sulfate).