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

Total Questions: 50

11. In copper oxide (CuO) and carbon monoxide (CO) reaction, the reducing agent is: [RRB Group D 24/09/2018 (Evening)]

Correct Answer: (b) CO
Solution:

Copper oxide (CuO) is an oxidizing agent. Chemical reaction: CuO + CO → Cu + CO₂ .

12. What is the action of dilute hydrochloric acid on marble chips? [RRB Group D 24/09/2018 (Evening)]

Correct Answer: (a) CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
Solution:

Marble chips, calcium carbonate (CaCO₃) react with hydrochloric acid (HCl) to produce carbon dioxide gas (CO₂) and Calcium chloride solution (CaCl₂).

13. Which of the following metals reacts violently with cold water? [RRB Group D 24/09/2018 (Evening)]

Correct Answer: (c) Sodium
Solution:

The reaction is so violent and exothermic in the case of sodium that the evolved hydrogen immediately catches fire. Chemical reaction: 2Na (s) + 2H₂O (l) → 2NaOH (aq) + H₂ (g).
Metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.

14. Fe + CuSO4 → FeSO4 + Cu. The given reaction is an example of ________. [RRB Group D 25/09/2018 (Morning)]

Correct Answer: (c) Displacement reaction
Solution:

A reaction in which a more reactive element takes the place of a less reactive element in a chemical compound is called Displacement Reaction. Fe + CuSO₄ → FeSO₄ + Cu.
This reaction is a classic example of a displacement reaction, where a more reactive metal (iron) displaces a less reactive metal (copper) from its compound.

15. A catalyst is a substance that: [RRB Group D 25/09/2018 (Afternoon)]

Correct Answer: (d) Speeds up the reaction
Solution:

A catalyst is a substance that speeds up a chemical reaction, or lowers the temperature or pressure needed to start one, without itself being consumed during the reaction. Catalysis is the process of adding a catalyst to facilitate a reaction.

16. Bleaching powder contains ________ bleaching agent. [RRB Group D 26/09/2018 (Morning)]

Correct Answer: (a) Chlorine
Solution:

Bleaching powder, or calcium hypochlorite (Ca(OCl)₂), contains chlorine as its primary bleaching agent. Upon reacting with moisture or acids, chlorine is released, giving it whitening and oxidizing properties.

17. If copper metal is immersed in a mixture of zinc sulphate : [RRB Group D 26/09/2018 (Morning)]

Correct Answer: (a) There is no reaction.
Solution:

In the reaction between zinc sulfate (ZnSO₄) and copper (Cu), no products form because zinc, being more reactive, prevents copper from displacing it from its salt solution.

18. When sodium sulphate solution is mixed with barium chloride solution then: [RRB Group D 26/09/2018 (Evening)]

Correct Answer: (d) barium sulphate is formed
Solution:

Barium sulphate is the inorganic compound with the chemical formula BaSO₄ . When an aqueous solution of barium chloride is added to sodium sulphate solution, a white precipitate of barium sulphate is formed. The balanced chemical equation for this reaction is: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl.

19. ______ is displaced when zinc is added to the solution of copper sulphate. [RRB Group D 27/09/2018 (Morning)]

Correct Answer: (a) Copper
Solution:

Zinc is more reactive than copper hence copper is displaced by Zinc. Displacement reaction - A chemical reaction in which a less reactive element is displaced from its compound by a more reactive element. When zinc metal is added to a solution of copper sulphate (CuSO₄), the blue colour of the latter changes to colourless as zinc sulphate (ZnSO₄) is formed.
Reaction - Zn + CuSO₄ → ZnSO₄ + Cu.

20. Which of the following equations represents a skeletal chemical equation? [RRB Group D 27/09/2018 (Evening)]

Correct Answer: (a) Mg + O₂→ MgO
Solution:

Balanced Equation : 2Mg + O₂ → 2MgO. Skeletal chemical equations are described as chemical equations that are not balanced. Chemical Reactions - In this reaction, the bonds are broken within reactant molecules, and new bonds are formed within product molecules in order to form a new substance. Types of reactions - Combustion, Decomposition, Neutralization, Redox, Precipitation or Double-Displacement Synthesis.