Chemistry (Part-II) (Railway)

Total Questions: 50

21. What is the radius of an atom used to measure? [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) Atomic number
(2) Atomic mass
(3) Atomic size
(4) Atomicity

Correct Answer: (3) Atomic size

Solution:Atomic radius is a term used to describe the size of an atom. It is described as the distance from its nucleus to its outermost electrons. Although it is impossible to know the exact position of these electrons, a very close approximation of the radius of an atom can still be determined by measuring the distance from its nucleus to that of another atom it is bonded with.

22. If the valency of Aluminium is 3 and that of Oxygen is 2, then the chemical formula of Aluminium oxide is: [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) (AIO)₃⁺²
(2) AIO₂
(3) Al₃O₂
(4) Al₂O₃

Correct Answer: (4) Al₂O₃

Solution:Aluminum (Al) react with Oxygen gas (O₂) to form aluminum oxide, Al₂O₃. The balanced chemical equation for this reaction is:

4Al + 3O₂ → 2Al₂O₃

This reaction is an example of synthesis reaction, a reaction in which two or more reactants combine to form only one product.

23. Which of the following elements has the unique ability to form bonds with other atoms of the same element giving rise to large molecules? [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) Aluminium
(2) Hydrogen
(3) Carbon
(4) Nitrogen

Correct Answer: (3) Carbon

Solution:Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation. Catenation gives rise to large number of molecules and compounds having long chains of carbon, branched chains of carbon or carbon atoms arranged in rings and linked by single, double or triple bonds.

24. Newlands arranged ________ the then known elements in his [RRB ALP & Technician Exam. 29.08.2018 Shift-I]

(1) 63
(2) 56
(3) 58
(4) 17

Correct Answer: (2) 56

Solution:John Newlands put forward his law of octaves in 1864 in which he arranged all the known 56 elements into a table in order of relative atomic mass. He started with the element having the lowest atomic mass (such as hydrogen) and ended at thorium, which was the 56th element (at his time).

25. Which of the following solutions do not conduct electricity? [RRB ALP & Technician Exam. 29.08.2018 Shift-I]

(1) Sodium hydroxide solution
(2) Glucose solution
(3) Acetic acid solution
(4) Hydrochloric acid solution

Correct Answer: (2) Glucose solution

Solution:When an acid, a base, or a salt is dissolved in water. the molecules break into electrically charged particles called ions. Solutions with ions conduct electricity. However, Glucose is not an electrolyte. When it is dissolved in water, it doesn't dissociate into ions which is necessary for the conduction of electricity.

26. Which of the following is used in the preparation of vinegar? [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) Methanol
(2) Ethanol
(3) Ethanoic acid
(4) Acetic acid

Correct Answer: (4) Acetic acid

Solution:Acetic acid is a colourless liquid organic compound with the chemical formula CHCOOH. When undiluted, it is sometimes called glacial acetic acid. Vinegar is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water.

27. Common metals arranged in order of their decreasing reactivity is known as: [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) Conductivity
(2) Electrolytic reduction
(3) Activity series
(4) Reactivity

Correct Answer: (3) Activity series

Solution:The activity series is a chart of metals listed in order of declining relative reactivity. The top metals are more reactive than the metals on the bottom. The activity series of metals is an empirical tool used to predict products in displacement reactions and reactivity of metals with water and acids in replacement reactions and are extraction. It can be used to predict the products in similar reactions involving a different metal.

28. Oxides of metals are basic in nature, that is, they combine with acids to form salt and water. Select the odd metal oxide from the following ones. [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) CaO
(2) MgO
(3) Al₂O₃
(4) Na₂O

Correct Answer: (3) Al₂O₃

Solution:Aluminium oxide (Al₂O₃) is an amphoteric substance, meaning it can react with both acids and bases, such as hydrofluoric acid and sodium hydroxide, acting as an acid with a base and a base with an acid, neutralising the other and producing a salt.

29. Select the INCORRECT set of Molecular Formula -IUPAC Name Common Name from the following options. [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) C₄H₉OH — Butanol — Butyl Alcohol
(2) CH₃OH — Methanol — Methyl Alcohol
(3) C₃H₈OH — Propanol — Propyl Alcohol
(4) C₂H₅OH — Ethanol — Ethyl Alcohol

Correct Answer: (3) C₃H₈OH — Propanol — Propyl Alcohol

Solution:Propionaldehyde or propanal, is the organic compound with the formula CH₂CH₂CHO. It is a saturated 3-carbon aldehyde and is a structural isomer of acetone.

30. Is Baking soda chemically different from Baking powder? [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) Yes. Baking soda is Sodium bicarbonate while Baking powder is a mixture of Sodium bicarbonate and Tartaric acid.
(2) Yes, Baking soda is Sodium bicarbonate while Baking powder is Calcium Carbonate.
(3) Yes. Baking soda is Sodium Carbonate while Baking powder is Sodium Bi-carbonate.
(4) No, they are identical chemically.

Correct Answer: (1) Yes. Baking soda is Sodium bicarbonate while Baking powder is a mixture of Sodium bicarbonate and Tartaric acid.

Solution:Baking soda is pure sodium bicarbonate. Baking powder is a mixture of a carbonate (or bicarbonate) and a weak acid. So, in addition to sodium bicarbonate, the baking powder also contains a drying agent (like starch) and an acidifying agent (like cream of tartar or potassium bitartrate).

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