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

Total Questions: 50

41. When carbon dioxide is dissolved in an aqueous solution of sodium hydroxide, the mixture reacts to give aqueous sodium carbonate and liquid water. The correct balanced equation for this reaction is: [RRC Group D 06/10/2022 (Evening)]

Correct Answer: (b) 𝐢𝑂₂(aq) + 2NaOH(aq) β†’ π‘π‘Žβ‚‚πΆπ‘‚β‚ƒ (aq) + 𝐻₂𝑂 (l)
Solution:

Chemical equation: The symbolic representation of a chemical reaction in the form of symbols and formulae. Balanced chemical equation: An equation where the number of atoms of each type in the reaction is the same on both reactants and product sides.
Example of a balanced chemical equation; 2Hβ‚‚ + Oβ‚‚ β†’ 2Hβ‚‚O. Sodium hydroxide (NaOH) is used to produce soaps, rayon, paper, products that explode, dyes, and petroleum products. Sodium carbonate (Naβ‚‚CO₃) is used as a water softener.

42. Redox reaction is the reaction in which_________. [RRC Group D 06/10/2022 (Evening)]

Correct Answer: (b) oxidation and reduction occur simultaneously
Solution:

An oxidation-reduction (redox) reaction is a type of chemical reaction that involves transfer of electrons between two species. Redox reactions are common and vital to some of the basic functions of life, including photosynthesis, respiration, combustion, and corrosion or rusting.
Reduction: Gain of electrons; Hydrogen is gained or oxygen is lost. Example - CuO + Hβ‚‚ β†’ Cu + Hβ‚‚O. Oxidation: Loss of electrons; Hydrogen is lost or oxygen is gained. Example - 2Cu + Oβ‚‚β†’ 2CuO.

43. Formation of carbon dioxide from carbon monoxide and oxygen is an example of ____ . [RRC Group D 07/10/2022 (Morning)]

Correct Answer: (c) combination reaction
Solution:

Combination Reaction occurs when two or more elements or compounds combine to form a single products. Examples: 2CO (carbon monoxide) + Oβ‚‚ (oxygen) 2COβ‚‚ β†’ (carbon dioxide).

44. Which reaction occurs when a student adds a few drops of lemon in milk? [RRC Group D 07/10/2022 (Morning)]

Correct Answer: (d) Precipitation reaction
Solution:

A chemical reaction occurring in an aqueous solution where two ionic bonds combine, resulting in the formation of an insoluble substance. Example - When a few drops of lemon juice are added to milk, chemical change takes place resulting in the formation of lactic acid which turns the milk sour and changes it into 'paneer'. Hydrolysis - A molecule of water breaks one or more chemical bonds that exists between a particular substance. Examples - dissolving a salt of a weak acid or base in water.

45. How many atoms of oxygen are on the left side of the given chemical equation? [RRC Group D 07/10/2022 (Morning)]

Ca(OH)β‚‚ + C𝑂₂ β†’ CaC𝑂₃ + 𝐻₂O

Correct Answer: (b) 4
Solution:

Ca(OH)β‚‚ (calciumΒ  hydroxide) + C𝑂₂ (Carbon dioxide) β†’ CaC𝑂₃ (Calcium carbonate) +Β  𝐻₂OΒ (Hydrogen oxide). On the left side of equation 4 oxygen, 2 hydrogen, 1 carbon and 1 calcium atom are present. This reaction is an example of a double displacement reaction.

46. Which of the following reactions occurs when two ions are exchanged? [RRC Group D 07/10/2022 (Afternoon)]

Correct Answer: (c) Double substitution reaction
Solution:

Double substitution reaction - A reaction in which two groups of atoms (anions or cations) are exchanged simultaneously. A dissociation reaction is defined as a reaction in which larger molecules will dissociate to form new molecules by the use of some energy. It is reversible in nature.
A substitution reaction can be described as a reaction in which the functional group of one chemical compound is substituted by another group. Addition reaction- An organic reaction in which two or more molecules combine to generate a bigger one.

47. Which of the following statements is correct regarding substitution reaction? [RRC Group D 07/10/2022 (Evening)]

Correct Answer: (a) A more reactive metal displaces a less reactive metal from its aqueous solution.
Solution:

Displacement reaction - Reaction in which a more reactive element takes the place of a less reactive element in a chemical compound. Examples - Fe (iron) + CuSOβ‚„(copper sulphate) FeSOβ‚„ β†’ (ferrous sulphate)+ Cu (copper).

48. Which of the following reactions is an example of a displacement reaction? [RRC Group D 11/10/2022 (Morning)]

Correct Answer: (b) Zn (s) + CuS𝑂₄ (aq) ⟢ZnS𝑂₄ (aq) + Cu (S)
Solution:

n(s) + (copper sulphate) CuS𝑂₄ (aq) ⟢ (Zinc sulfate) ZnS𝑂₄ (aq) + Cu (s).

49. Consider the following reaction. [RRC Group D 11/10/2022 (Afternoon)]

Nπ‘Žβ‚‚ S𝑂₄ (aq) + BaC𝑙₂ (aq) β†’ BaS𝑂₄ (s) + 2NaCl

Correct Answer: (d) precipitation reaction
Solution:

It is a chemical reaction in which an insoluble solid, known as the precipitate, is formed is called a precipitation reaction. Precipitation reactions are usually double displacement reactions involving the production of a solid form residue called the precipitate.
When Barium chloride (BaC𝑙₂ ) solution is added to Sodium sulphate (Nπ‘Žβ‚‚S𝑂₄ ) solution a white precipitate of Barium sulphate (BaS𝑂𝑂₄) isΒ  formed along with Sodium chloride (2NaCl) solution.

50. The conversion of ethanol to acetic acid is an example of: [RRC Group D 11/10/2022 (Afternoon)]

Correct Answer: (b) oxidation reaction
Solution:

Chemical reaction of ethanol to acetic acid :- Ethyl alcohol or ethanol can be converted to acetic acid by the oxidation reaction. Oxidation means addition of oxygen to the compound or removal of hydrogen or removal of electrons from the compound and the equilibrium is represented as:

Reduction: process in a chemical reaction in which a chemical species
acquires electrons and its oxidation number lowers. Redox reaction: those
reactions in which reduction and oxidation both take place simultaneously. Example of redox reaction - PbO (Lead oxide) + Hβ‚‚
(Hydrogen) β†’ Pb (Lead) + Hβ‚‚O (Water). In this above reaction, hydrogen is oxidized to water and lead oxide is reduced to lead.