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

Total Questions: 50

21. The oxidation reaction that produces heat and light is: [RRB Group D 28/09/2018 (Evening)]

Correct Answer: (c) combustion
Solution:

Burning coal, methane gas, and sparklers are all common examples of combustion reactions. Essentially, any reaction that involves burning something is a combustion reaction.

22. Which metal oxide is an amphoteric oxide? [RRB Group D 28/09/2018 (Evening)]

Correct Answer: (b) Aluminium
Solution:

Metal oxides that react with both acids as well as bases to produce salts and water are known as amphoteric oxides. Many metals (such as zinc, tin, lead, aluminum, and beryllium) form amphoteric oxides or hydroxides.

23. Which of the following is not an example of a chemical change? [RRB Group D 01/10/2018 (Afternoon)]

Correct Answer: (c) Change of water into water vapor
Solution:

Change of water into water vapor - This is a type of physical change called evaporation. Chemical changes: The changes in which new substances with new chemical properties are formed.

24. Which of the following statements about the reaction below are INCORRECT? [RRB Group D 03/10/2018 (Morning)]

2PbO(s) + C(s) β†’ 2Pb(s) + COβ‚‚(g)
A. Carbon di-oxide is getting oxidised
B. Lead is getting reduced
C. Carbon is oxidised
D. Lead oxide is getting reduced

Correct Answer: (b) A and B
Solution:

Carbon dioxide (COβ‚‚) is formed as a product, which means carbon (C) has gained oxygen. This process is oxidation of carbon. Lead oxide (PbO) is one of the reactants, and it is being converted to lead (Pb). Lead is losing oxygen, which is a reduction process.

25. In the following chemical reaction, which product is represented by X ? [RRB Group D 03/10/2018 (Evening)]

πΆπ‘ŽπΆπ‘‚β‚ƒ β†’ β„Žπ‘’π‘Žπ‘‘ β†’ πΆπ‘Žπ‘‚ + 𝑋

Correct Answer: (c) 𝐢𝑂₂
Solution:

The given reaction is a Decomposition reaction. Calcium Carbonate (πΆπ‘ŽπΆπ‘‚β‚ƒ ) - Limestone. Calcium oxide (πΆπ‘Žπ‘‚) - Quicklime.

26. _________ does not react with diluted HCI. [RRB Group D 03/10/2018 (Evening)]

Correct Answer: (b) copper
Solution:

Copper metal does not react with dilute hydrochloric acid as they come after hydrogen in the activity series, i.e. they can't replace hydrogen from hydrochloric acid.

27. Which of the given reactions is opposite to combination reactions? [RRB Group D 04/10/2018 (Afternoon)]

Correct Answer: (c) decomposition
Solution:

Decomposition reaction: A type of chemical reaction in which a compound breaks down into two or more substances. Example: 2NaH β†’ Na + Hβ‚‚ .

28. MnOβ‚‚+ 4HCl β†’ MnClβ‚‚ + Hβ‚‚O + Clβ‚‚ . The given reaction is an example of a _____ reaction. [RRB Group D 05/10/2018 (Morning)]

Correct Answer: (a) redox
Solution:

redox (reduction-oxidation) reaction - Transfer of electrons between reactants, where one species is reduced (gains electrons) and another is oxidized (loses electrons), leading to changes in their oxidation states.

29. _______ reacts vigorously with water to form slaked lime. [RRB Group D 05/10/2018 (Afternoon)]

Correct Answer: (b) CaO
Solution:

The chemical reaction involved in formation of slaked lime: CaO (calcium oxide) + Hβ‚‚O (water) β†’ Ca(OH)β‚‚ (slaked lime). When calcium oxide, also known as quicklime, comes into contact with water, it undergoes a highly exothermic (heat-releasing) reaction, producing slaked lime (calcium hydroxide). CaClβ‚‚ - Calcium chloride. CaCO₃ - Calcium carbonate.

30. While white washing, Ca(OH)β‚‚ reacts slowly with the________ in the air to form a thin layer of CaCO₃ on the walls. [RRB Group D 09/10/2018 (Morning)]

Correct Answer: (D) COβ‚‚
Solution:

Calcium carbonate (CaCO₃) also known as 'limestone' forms 2 to 3 days after white washing, and thus we get a shiny finish on the wall. Reaction: Ca(OH)β‚‚ + COβ‚‚ β†’ CaCO₃ + Hβ‚‚O. Calcium hydroxide (Ca(OH)β‚‚) also called slaked lime.