Chemistry (Part-II) (Railway)

Total Questions: 50

31. How many moles are present in 60g of He? [RRB ALP & Technician Exam. 29.08.2018 Shift-III]

(1) 25 moles
(2) 10 moles
(3) 15 moles
(4) 12 moles

Correct Answer: (3) 15 moles

Solution:Given, mass of He (m) = 60g
Molar mass of He (M) = 4g
So number of moles in 60 g of helium (n) = m/M
n = 60/4
n = 15
⇒ 15 moles are present in 60g of He.

32. The chemical formula of Sodium Carbonate is: [RRB ALP & Technician Exam, 30.08.2018 Shift -I]

(1) Na₃CO₂
(2) Na₂CO
(3) NaCO₃
(4) Na₂CO₃

Correct Answer: (4) Na₂CO₃

Solution:Sodium carbonate (also known as washing soda, soda ash and soda crystals) is the Inorganic compound with the formula Na₂CO₃ and its various hydrates. It is an ionic compound a sodium salt of carbonic acid, and is composed of two sodium cations (Na⁺) and a carbonate anion (CO₃⁻). It is formed in the Solvay process.

33. Which of the following is used to get relief when you have been stung by a honeybee? [RRB ALP & Technician Exam. 30.08.2018 Shift-I]

(1) Common salt
(2) Baking soda
(3) Acetic acid
(4) Washing soda

Correct Answer: (2) Baking soda

Solution:A paste made of baking soda and water can help neutralize bee venom to reduce pain, itching, and swelling. This is because rubbing a mild base like baking soda solution on the stung area neutralizes the acidic liquid injected by the bee. Baking soda is also known as sodium bicarbonate (NaHCO₃).

34. Which of the following is added to iron to make iron hard and strong? [RRB ALP & Technician Exam, 30.08.2018 Shift-I]

(1) Zinc
(2) Copper
(3) Carbon
(4) Sodium

Correct Answer: (3) Carbon

Solution:Adding carbon to iron makes the latter stronger and tougher. Carbon strengthens iron by distorting its crystal lattice. This feature of carbon is used in making steel from iron. The effectiveness of adding carbon to strengthen metal depends on the lathice spacing, crystal structure and possible chemical effects between the metal and the carbon.

35. The percentage of water of crystallisation in washing soda is ________ . [RRB ALP & Technician Exam, 30.08.2018 Shift -I]

(1) 1.80
(2) 37.06
(3) 10.6
(4) 62.9

Correct Answer: (4) 62.9

Solution:We know Washing Soda
(Hydrous) is Na₂CO₃.10H₂O.
The molecular weight of Na₂
CO₃.10H₂O = 2 (23) + (12) + 3
(16) + 10 (18) = 46 + 12 + 48 +
180 = 286
The molecular weight of H₂O
in Na₂CO₃.10H₂O
= 10 (18) = 180
So, the percentage of water of
crystallization in washing
soda =

w / W% = 180 / 286 × 100

→ w/ W% = 0.62937 × 100

→ w / W% = 62.937

36. Brass is an alloy made of: [RRB ALP & Technician Exam, 30.08.2018 Shift-III]

(1) Copper and Iron
(2) Copper and Tin
(3) Copper and Aluminium
(4) Copper and Zinc

Correct Answer: (4) Copper and Zinc

Solution:Brass is an alloy made primarily of copper and zinc. The proportions of the copper and zinc are varied to yield many different kinds of brass. Basic modern brass is 67% copper and 33% zinc.

37. Which of the following has the largest sized atoms? [RRB ALP & Technician Exam, 30.08.2018 Shift-III]

(1) AI
(2) S
(3) P
(4) Si

Correct Answer: (1) AI

Solution:

Element	Atomic radius
Aluminium	143
Sulfur	103
Phosphorous	110
Silicon	118

38. Which gas is released when bleaching powder is added to water? [RRB ALP & Technician Exam, 30.08.2018 Shift-III]

(1) Hydrogen
(2) Carbon Dioxide
(3) Chlorine
(4) Carbon Monoxide

Correct Answer: (3) Chlorine

Solution:Bleaching powder is a chemical compound with the formula Ca(CIO)₂ (calcium hypochlorite). When exposed to air, bleaching powder gives a smell of chlorine. This is because of bleaching powder reacts with carbon dioxide from the atmosphere to produce calcium carbonate and chlorine. When water is added to it, chlorine gas is liberated.

39. Which of the following statements is INCORRECT? [RRB ALP & Technician Exam, 30.08.2018 Shift-III]

(1) The basic nature of Sodium Hydroxide (NaOH) is due to the presence of sodium ions
(2) Lemon contains citric acid.
(3) Nonmetallic oxides are acidic in nature.
(4) Phenolphthalein turns pink in soap solution.

Correct Answer: (1) The basic nature of Sodium Hydroxide (NaOH) is due to the presence of sodium ions

Solution:Sodium hydroxide is completely ionic, containing sodium ions and hydroxide ions. The hydroxide ion makes sodium hydroxide a strong base, which reacts with acids to form water and the corresponding salts, e.g., with hydrochloric acid, sodium chloride is formed.

40. What is the molecular formula of Calcium Phosphate? [RRB ALP & Technician Exam, 30.08.2018 Shift-III]

(1) Ca(PO₄)₂
(2) Ca₃(PO₄)₂
(3) Ca₅(PO₄)₂
(4) CaPO₄

Correct Answer: (2) Ca₃(PO₄)₂

Solution:Calcium phosphate (Ca₃(PO₄)₂) is the main mineral found in human bone and teeth and is considered as a highly biocompatible inorganic biomaterial. Its molecular formula is Ca₅(PO₄)₂ + OH or Ca₃(PO₄)₂.

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