CHEMISTRY (Part-I) (Railway)

Total Questions: 50

11. Which of the following gases is used to prevent food material from getting oxidised? [RRB ALP & Technician Exam, 10.08.2018 Shift-1]

(1) Hydrogen
(2) Oxygen
(3) Chlorine
(4) Nitrogen

Correct Answer: (4) Nitrogen

Solution:Nitrogen, being an antioxidant, is used to prevent food materials from getting oxidised. It is used in food packaging industry because it displaces oxygen which can carry moisture. Thus, Nitrogen is able to dramatically increase the shelf life of food products.

12. Among chemical properties. Mendeleev concentrated on the compounds formed by the elements with: [RRB ALP & Technician Exam,10.08.2018 Shift-1]

(1) Carbon and Hydrogen
(2) Carbon and Sodium
(3) Hydrogen and Sodium
(4) Hydrogen and Oxygen

Correct Answer: (4) Hydrogen and Oxygen

Solution:Mendeleev examined the relationship between atomic weights of the elements and their physical and chemical properties. Among chemical properties, Mendeleev mainly concentrated on the compounds formed by the elements with hydrogen and oxygen because they are highly reactive and hence formed compounds with almost all the elements.

13. Ammonium nitrate, on thermal decomposition, produces: [RRB ALP & Technician Exam,10.08.2018 Shift-III]

(1) NH₃ and NO₂
(2) NH₃ and NO
(3) N₂ and H₂O
(4) N₂O and H₂O

Correct Answer: (4) N₂O and H₂O

Solution:Ammonium nitrate on heating decomposes to give nitrous oxide (N₂O) (laughing gas) and water (H₂O).

14. Which one of the following triad represents Dobereiner's Triad? [RRB ALP & Technician Exam. 10.08.2018 Shift-III]

(1) Li, Na, K
(2) Na, Sr, Br
(3) Li, K, Na
(4) Li, Ca, Cl

Correct Answer: (1) Li, Na, K

Solution:A triad is a grouping of three elements in order of atomic mass. Dobereiner's Law of Triads deals with putting three elements in order of atomic weight. The average of the first and third elements' atomic masses is the atomic mass of the second element.

Examples:

Li, Na, K

Ca, Sr, Ba

Cl, Br, I

15. Which of the following gases turns lime water milky? [RRB ALP & Technician Exam,10.08.2018 Shift-III]

(1) O₃
(2) CO₂
(3) O₂
(4) CO

Correct Answer: (2) CO₂

Solution:Carbon dioxide (CO₂) turns lime water milky due to the formation of insoluble calcium carbonate, CaCO₃. Sulphur dioxide (SO₂) also does the same, but slowly, as it reacts with calcium hydroxide to form insoluble calcium sulphite.

16. Which of the following is not the properties of an ionic compound? [RRB ALP & Technician Exam,10.08.2018 Shift-III)]

(1) Soluble in water and insoluble in petrol
(2) High melting and boiling points
(3) Low melting and boiling points
(4) Solid and hard

Correct Answer: (3) Low melting and boiling points

Solution:An ionic bond is formed when there is a large electronegativity difference between the elements participating in the bond. Ionic compounds form crystal lattices rather than amorphous solids. They have low melting points and boiling points. They have higher enthalpies of fusion and vaporization than molecular compounds.

17. The gas evolved when sodium carbonate reacts with hydrochloric acid is_______ . [RRB ALP & Technician Exam,3.08.2018 Shift-I]

(1) Hydrogen
(2) Chlorine
(3) Hydrogen Chloride
(4) Carbon dioxide

Correct Answer: (4) Carbon dioxide

Solution:Hydrochloric acid (HCl) reacts with sodium carbonate (Na₂CO₃), forming sodium chloride (NaCl), water (H₂O). and carbon dioxide (CO₂). Brisk effervescence is seen due to carbon dioxide gas formation. The balanced chemical reaction is as follows: 2HCl (aq)+Na₂CO₃ (aq) → 2 NaCl (aq) + H₂O (l)+CO2 (g)

18. In the given reaction: SnCl₂ + 2HgCl₂ → Hg₂Cl₂ + SnCl₄ [RRB ALP & Technician Exam,13.08.2018 Shift-I]

(1) HgCl₂ is oxidised
(2) SnCl₂ is oxidised
(3) Hg₂Cl₂ is oxidised
(4) SnCl₂ is reduced

Correct Answer: (2) SnCl₂ is oxidised

Solution:In the given reaction 2HgCl₂ + SnCl₂ = Hg₂Cl₂ + SnCl₄. Tin (II) Chloride
(SnCl₂) reacts with Mercury (II) Chloride (HgCl₂) to produce
Mercury (I) Chloride (Hg₂Cl₂) and Tin (IV) Chloride (SnCl₄).
In the reaction, 2 moles of HgCl₂ give 1 mole of Hg₂Cl₂.
The oxidation state of Hg in HgCl₂ is +2 whereas in Hg₂Cl₂
is +1. And the oxidation state of Sn in SnCl₂ is +2 whereas
in SnCl₄ is +4. Hence, HgCl₂ is reduced whereas SnCl₂ is
oxidized.

19. What are the products formed during photosynthesis? [RRB ALP & Technician Exam,13.08.2018 Shift-1]

(1) Glucose. Water and Oxygen
(2) Glucose and Oxygen
(3) Starch and Oxygen
(4) Starch. Water and Oxygen

Correct Answer: (1) Glucose. Water and Oxygen

Solution:Photosynthesis is the name given to the set of chemical reactions performed by
plants to convert energy from the sun into chemical energy in the form of sugar. Specifically, plants use energy from sunlight to react carbon dioxide and water to produce sugar (glucose) and oxygen. Many reactions occur, but the overall chemical reaction for photosynthesis is:
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Carbon Dioxide + Water + Light yields Glucose + Oxygen

20. Which of the following is NOT a noble gas? [RRB ALP & Technician Exam. 13.08.2018 Shift-1]

(1) Radon
(2) Krypton
(3) Xenon
(4) Hydrogen

Correct Answer: (4) Hydrogen

Solution:Noble gas refers to any of the seven chemical elements that make up Group 18 (VIII A) of the periodic table. The elements are helium (He), neon (Ne), argon (Ar), krypton (Kr). xenon (Xe), radon (Rn), and Oganesson (Og). These elements are all non-metals with very low chemical reactivity.

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