Chemistry (Part-X) (Railway)

Total Questions: 23

11. The conversion of ethanol to acetic acid is an example of: [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-II)]

(1) oxidation reaction
(2) substitution reaction
(3) addition reaction
(4) reduction reaction

Correct Answer: (1) oxidation reaction

Solution:Ethyl alcohol or ethanol can be converted to acetic acid by the oxidation reaction that involves a two-step process.

• In the first step. hydrogen is removed from ethanol that gives acetaldehyde as a product. CH₃ -CH₂ -OH (Ethanol) → CH₃ - CHO (Acetaldehyde)

In the second step, acetaldehyde undergoes again oxidation and forms acetic acid or ethanoic acid as the product. In this step, oxygen is added to acetaldehyde and produces acetic acid as the product.

CH₃ - CHO (Acetaldehyde) → CH₃ - COOH (Acetic acid)

12. Carbon makes strong bonds with other elements. which of the following is the correct explanation for the given statement? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-II)]

(1) A carbon nucleus holds the shared pairs of electrons strongly due to its small size.
(2) A carbon nucleus holds the shared pairs of electrons weakly due to its small size.
(3) A carbon nucleus hold the shaed paris of electrons strongly due to is large size.
(4) Acarbon nucleus hold the shared pairs of electrons weakly due to its large size.

Correct Answer: (1) A carbon nucleus holds the shared pairs of electrons strongly due to its small size.

Solution:A carbon nucleus holds the shared pairs of electrons strongly due to its small size.

• Carbon has 4 valence electrons, so it is capable of forming covalent bonds with 4 other atoms.

• The small atomic size of carbon enables it's nucleus to strongly hold on to the shared pair of electrons.

• Hence, carbon forms strong bonds with most other elements.

13. Which of the following properties remain same while moving down the group in the periodic table? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-II)]

(1) Non-metallic
(2) Valency
(3) Metallic character
(4) Atomic size

Correct Answer: (2) Valency

Solution:The electrons that are present in the outermost shell of an isolated atom of an element are known as valence electrons.

• On moving down the group. there is no change in the number of valence electrons as the valency for all the elements present in the same group is same.

14. The substance which doctors use as plaster of supporting fractured bones in the right position is: [RRB Group 'D' CHT Exam, 11.10.2022 (Shift-II)]

(1) Na₂CO₃ . 10H₂O
(2) CaSO₄ . ₁/₂H₂O
(3) CuSO₄ . 5H₂O
(4) CaSO₄ . 2H₂O

Correct Answer: (2) CaSO₄ . ₁/₂H₂O

Solution:Plaster of Paris (CaSO₄ . ₁/₂H₂O) is quick-setting gypsum plaster consisting of a fine white powder (calcium sulfate hemihydrate), which hardens when moistened and allowed to dry.

• It is used in setting fractured bones in hospitals, in dentistry to make casts, for making toys, decorative materials, cheap ornaments, cosmetics, black-board, chalk, and casts for statues.

15. Select the correct Dobereiner's triads from the given sets. [RRB Group 'D' CBT Exam. 11.10.2022 (Shift-II)]

(1) Ca, Sr, Ba
(2) Li, Na, Ba
(3) Ca, sr, I
(4) F, Cl, Br

Correct Answer: (1) Ca, Sr, Ba

Solution:The set of elements: calcium (Ca), strontium (Sr) and barium (Ba), with atomic masses 40, 88 and 137 respectively form a Dobereiner 's triads.

• This is because they have similar chemical properties, and the atomic mass of strontium is approximately equal to the average of the atomic masses of calcium and barium.

16. Bleaching powder is formed when dry slaked lime reacts with__________. [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) bromine
(2) hydrogen
(3) nitrogen
(4) chlorine

Correct Answer: (4) chlorine

Solution:Calcium oxychloride Ca(OCl)₂ is known as bleaching powder.

• It is produced industrially by treating dry slaked lime Ca(OH)₂,with chlorine gas.

• 2CI₂ + 2Ca(OH)₂ → Ca(OCI)₂ + CaCl₂ + 2H₂O

17. Which of the following with respect to the Modern Periodic Table is NOT correct? [RRB Group 'D' CBT Exam,11.10.2022 (Shift-III)]

(1) It has 18 groups and 7 periods
(2) The number of shells increases as we go down the group.
(3) The elements present in the same group have same number of valence electrons.
(4) Na, Mg and S belongs to the 4th period of the Modern Periodic Table.

Correct Answer: (4) Na, Mg and S belongs to the 4th period of the Modern Periodic Table.

Solution:Na, Mg, Al, Si, P, S, Cl and Ar belong to the third period of the Modern Periodic Table.

• This is because electrons in the atoms of these elements are filled in K, L and M shells.

18. How many number of bonds do the single carbon atom form? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-II)]

(1) 1
(2) 3
(3) 2
(4) 4

Correct Answer: (4) 4

Solution:In a typical bond two electrons are shared, one from each of the atoms involved.

• Carbon has four such sharable electrons of its own, so it tends to form four bonds to other atoms.

• Graphite, Diamand and fullerenes are the allotropes of carbon.

19. How many elements exist in nature according to Newlands law of octaves? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) 46
(2) 56
(3) 76
(4) 36

Correct Answer: (2) 56

Solution:According to Newlands' Law of Octaves, there are 56 elements exist in nature.

• In Newlands' Law of Octaves, every eighth element holds the properties as same that of the first element, when elements are arranged in increasing order of their atomic masses.

• Newlands' Law of Octaves was relevant to Calcium only, elements heavier than Calcium did not suit in his table.

20. Burning of natural gas is: [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) a substitution reaction
(2) a decomposition reaction
(3) an endothermic reaction
(4) an exothermic reaction

Correct Answer: (4) an exothermic reaction

Solution:A reaction in which heat is evolved is called exothermic reaction.

• Since natural gas is a fuel, hence the burning of natural gas releases a lot of heat.

• Hence, burning of natural gas is an exothermic reaction.

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