Chemistry (Part-IX) (Railway)

11. In each of the triads, how many elements were identified by Doberenier? [RRB Group 'D' CBT Exam, 29.09.2022 (Shift-III)]

(1) 6
(2) 3
(3) 9
(4) 2

Correct Answer: (2) 3

Solution:Dobereiner's observed that groups of three elements (triads) could be formed in which all the elements shared similar physical and chemical properties.

12. A student performs an experiment where he adds barium chloride to aluminium sulphate. Which of the following reaction is correct? [RRB Group 'D' CBT Exam, 29.09.2022 (Shift-III)]

(1) BaCl₂(aq) + Al₂(SO₄)₃(aq) → Ba(s) + SO₂(g) + 2AlCl₃(aq)
(2) BaCl₂(aq) + Al₂(SO₄)₃(aq) → 3BaSO₄(s) + Al(s) + Cl₂(g)
(3) 3BaCl₂(aq) + Al₂(SO₄)₃(aq) → BaSO₄(s) + AlCl₃(aq)
(4) 3BaCl₂(aq) + Al₂(SO₄)(aq) → 3BaSO₄(s) + 2AlCl₃(aq)

Correct Answer: (4) 3BaCl₂(aq) + Al₂(SO₄)(aq) → 3BaSO₄(s) + 2AlCl₃(aq)

Solution:3BaCl₂ + Al₂(SO₄)₃ → 3BaSO₄ + 2AlCl₃

13. Which of the following is the correct chemical formula of bleaching powder? [RRB Group 'D' CBT Exam, 29.09.2022 (Shift-III)]

(1) Ca(OH)₂
(2) CaCl₂
(3) CaO
(4) CaOCl₂

Correct Answer: (4) CaOCl₂

Solution:Bleaching Powder's chemical formula is CaOCl₂ and is called Calcium Oxychloride. It is prepared on dry slaked lime with Chlorine gas.

14. Which of the following statements is true about precipitation reaction? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

(1) Only water is formed.
(2) An insoluble salt is formed.
(3) Only hydrogen gas is formed.
(4) Only soluble solution is formed.

Correct Answer: (2) An insoluble salt is formed.

Solution:The term 'precipitation reaction' can be defined as "a chemical reaction occurring in an aqueous solution where two ionic bonds combine, resulting in the formation of an insoluble salt".
• These insoluble salts formed in precipitation reactions are called precipitates.
• One of the best examples of precipitation reactions is the chemical reaction between potassium chloride and silver nitrate, in which solid silver chloride is precipitated out.
• AgNO₃(aqueous) + KCl(aqueous) → AgCl(precipitate) + KNO₃(aqueous)

15. Select the correct increasing order of atomic radii. [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

(1) Li < B < Be < Rb < K
(2) B < Be < Rb < Li
(3) Li < Be < B < Rb
(4) B < Be < Li < Rb

Correct Answer: (4) B < Be < Li < Rb

Solution:Atomic size gradually decreases from left to right across the period of elements. Down the group, atomic radius increases.
• Lithium, Beryllium, and Boron lie in the same 1st period. Therefore, moving from left to right, the atomic radius will decrease. Hence, the correct order would be Li > Be > B.
• Rubidium lies below the lithium in the group; therefore, it has a larger atomic radius. So, the correct sequence will be Rb > Li > Be > B or B < Be < Li < Rb.

16. In the given reaction which substance undergoes oxidation? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

2Cu + O₂ → 2CuO

(1) Only copper
(2) Copper oxide
(3) Copper and oxygen
(4) Only oxygen

Correct Answer: (3) Copper and oxygen

Solution:2Cu + O₂ → 2CuO or the formation of Copper oxide from Copper in the presence of Oxygen is an oxidation reaction.
• In this reaction, the oxidation of copper is taking place.
• A copper atom loses two electrons while each oxygen atom in an oxygen molecule gains two electrons from the copper atom.
• So, Copper gets oxidised, while Oxygen gets reduced.

17. Which of the following compounds contains only one carbon-carbon single bond? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

(1) Ethane
(2) Propane
(3) Butane
(4) Methane

Correct Answer: (1) Ethane

Solution:Ethane (C₂H₆) is structurally the simplest hydrocarbon that contains a single carbon-carbon bond.

• In Ethane, there are two carbons that share a single bond. This allows the two methyl groups to rotate with respect to each other.

18. Which of the following statements is/are correct? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

A. pH value of saliva: 6.2 - 8
B. pH value of pure blood: 7.35 - 7.45
C. pH value of pure water: 9

(1) Only B
(2) Only C
(3) B and C
(4) A and B

Correct Answer: (1) Only B

Solution:

Saliva has a pH normal range of 6.2–7.6 with 6.7 being the average pH.

• Pure water has a pH of 7 and is considered "neutral" because it has neither acidic nor basic qualities.

• pH value occurs between 0 to 14. If pH value is less than 7 is acidic, whereas pH value greater than 7 is alkaline or base.

19. Ozone at the higher levels of the atmosphere is a product of UV radiation acting on ____ molecule. [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

(1) carbon dioxide (CO₂)
(2) carbon monoxide (CO)
(3) oxygen (O₂)
(4) sulphur dioxide (SO₂)

Correct Answer: (3) oxygen (O₂)

Solution:

Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen molecules.

• When high-energy ultraviolet rays strike ordinary oxygen molecules (O₂), they split the molecule into two single oxygen atoms, known as atomic oxygen.

• This oxygen atom then collides with O₂ molecules to form O₃ molecules, which is called ozone.

20. The path of a beam of light is visible through a ____ solution in which the size of the particles is relatively larger. [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

(1) water
(2) colloidal
(3) sugar
(4) salt

Correct Answer: (2) colloidal

Solution:

When the size of the colloidal particle is very large and a beam of light strikes such particles, they scatter the light falling on them in all directions, making the particle illuminated.

• This phenomenon is called the Tyndall effect.

Chemistry (Part-IX) (Railway)

11. In each of the triads, how many elements were identified by Doberenier? [RRB Group 'D' CBT Exam, 29.09.2022 (Shift-III)]

12. A student performs an experiment where he adds barium chloride to aluminium sulphate. Which of the following reaction is correct? [RRB Group 'D' CBT Exam, 29.09.2022 (Shift-III)]

13. Which of the following is the correct chemical formula of bleaching powder? [RRB Group 'D' CBT Exam, 29.09.2022 (Shift-III)]

14. Which of the following statements is true about precipitation reaction? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

15. Select the correct increasing order of atomic radii. [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

16. In the given reaction which substance undergoes oxidation? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

17. Which of the following compounds contains only one carbon-carbon single bond? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

18. Which of the following statements is/are correct? [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

19. Ozone at the higher levels of the atmosphere is a product of UV radiation acting on ____ molecule. [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

20. The path of a beam of light is visible through a ____ solution in which the size of the particles is relatively larger. [RRB Group 'D' CBT Exam, 30.09.2022 (Shift-II)]

Related Posts