CHEMISTRY (Part-IV) (Railway)

1. The__________ of an element is the number of hydrogen atoms that are joined or displaced with an atom of that element. [RRB RPF Constable Exam, 19.02.2019 Shift-II]

(1) Atomicity
(2) Isotopes
(3) Stability
(4) Valency

Correct Answer: (4) Valency

Solution:The combining capacity of an atom is known as its valency.

The number of bonds that an atom can form as part of a compound is expressed by the valency of the element.

2. Which of the following chemicals is known as dry ice? [RRB RPF Constable Exam, 19.02.2019 Shift-III]

(1) Lead Sulfate
(2) Nitrogen
(3) Dilute Nitric Acid
(4) Solid Carbon Dioxide

Correct Answer: (4) Solid Carbon Dioxide

Solution:Dry ice is solid carbon dioxide.

It gets this name because it does not melt into a liquid when heated.
It is commonly used as it does not have a liquid state and sublimates directly from solid state to gas state.

3. Which of the following is used in plastics? [RRB NTPC CBT-1 Exam, 30.12.2020 (Shift-1)]

(1) Butane
(2) Ethylene
(3) Krypton
(4) Ammonia

Correct Answer: (2) Ethylene

Solution:Ethylene is one of the world's most important chemicals, with over 60% of the raw material produced being used in the plastics Industry: HPDE, LDPE, PS and also PVC.

Ethylene is also the key feedstock for the production of ethylene oxide.

4. Which of the following is an ester? [RRB NTPC CBT-1 Exam, 21.01.2021 (Shift-II)]

(1) CH₃CHO
(2) CH₃COOH
(3) CH3COOC₂H₅
(4) CH3COCH₃

Correct Answer: (3) CH3COOC₂H₅

Solution:Esters are a functional group commonly encountered in organic Chemistry.

They are characterized by a carbon bound to three other atoms: a single bond to a carbon, a double bond to an oxygen, and a single bond to an oxygen.
The single bond oxygen is bond to another carbon.
Ester names are derived from the parent alcohol and the parent acid.

5. Which of the following elements is a liquid at room temperature? [RRB NTPC CBT-1 Exam, 21.01.2021 (Shift-II)]

(1) Sodium
(2) Chromium
(3) Titanium
(4) Mercury

Correct Answer: (4) Mercury

Solution:Mercury is both a liquid at room temperature (as it has a very low melting point of -39C) and a metal.

Unlike all other metals, mercury atoms do not share valence electrons with other neighboring atoms.
Rather, the electrons in mercury atoms are more tightly bound to nucleus and they move so quickly that they exhibit relativistic effects.

6. The Modern Periodic Table based ________ of the on elements. [RRB NTPC CBT-1 Exam, 22.01.2021 (Shift-I)]

(1) Equivalent Weight
(2) Valency
(3) Atomic Mass
(4) Atomic Number

Correct Answer: (4) Atomic Number

Solution:In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom.

7. What element is a greenish yellow gas with a characteristic smell at room temperature? [RRB NTPC CBT-1 Exam, 22.01.2021 (Shift-I)]

(1) Iodine
(2) Chlorine
(3) Carbon monoxide
(4) Hydrogen sulphide

Correct Answer: (2) Chlorine

Solution:Chlorine is a greenish yellow gas at room temperature and atmospheric pressure.

It is the second halogen in the periodic table, being a nonmetal in group 17.
It has a pungent, unpleasant, bleach-like odour that can be detected at low levels.
It is two and a half times heavier than air.

8. The four essential requirements for photosynthesis include: [RRB NTPC CBT-1 Exam, 23.01.2021 (Shift-I)]

(1) Carbon dioxide, minerals, chlorophyll and sunlight
(2) Chlorophyll, sunlight, carbon dioxide and water
(3) Chemicals, carbohydrates. water and chlorophyll
(4) Parasites, food, chlorophyll and oxygen

Correct Answer: (2) Chlorophyll, sunlight, carbon dioxide and water

Solution:Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy.

Sunlight, chlorophyll, carbon dioxide and water are the necessary conditions required for photosynthesis.

9. What is the mineral name of rock salt? [RRB NTPC CBT-1 Exam, 23.01.2021 (Shift-I)]

(1) Siderite
(2) Limonite
(3) Hematite
(4) Halite

Correct Answer: (4) Halite

Solution:Halite, commonly known as table salt or rock salt, is composed of sodium chloride (NaCl). The salt occurs in beds of sedimentary evaporite minerals.

10. The chemical name of blue vitriol is________. [RRB NTPC CBT-1 Exam, 25.01.2021 (Shift-I)]

(1) Aluminium
(2) Potassium nitrate
(3) Copper Sulphate
(4) Argon

Correct Answer: (3) Copper Sulphate

Solution:The blue vitriol is also known as the Cu(II) sulphate pentahydrate or crystalline copper sulphate.

It is used as a herbicide and a fungicide and also as an analytical reagent.