CHEMISTRY (Part-II) (Railway)

1. which one of the following oxides of Nitrogen is also as laughting gas? [RRB ALP & Technician Exam, 20.08.2018 Shift-I]

(1) NO
(2) N₂O
(3) NO₂
(4) N₂O

Correct Answer: (4) N₂O

Solution:Nitrous oxide (N₂O) is commonly known as laughing gas. It is known as "laughing gas" due to the euphoria effects of inhaling it. It is used In surgery and dentistry for its anesthetic and analgesic effects. It is also used as an oxidizer in rockets.

2. An element has an atomic weight of W and an atomic number of N. The number of protons in the nucleus of its atom is: [RRB ALP & Technician Exam, 20.08.2018 Shift-I]

(1) N
(2) W
(3) W-N
(4) W + N

Correct Answer: (1) N

Solution:Atomic number of a chemical element is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus. It determines the place of an element in the periodic table. In an uncharged atom, the atomic number is also equal to the number of electrons.

3. The tenth element in the New-land's periodic classification resembles the: [RRB ALP & Technician Exam, 20.08.2018 Shift-I]

(1) Third
(2) Ninth
(3) Fourth
(4) First

Correct Answer: (1) Third

Solution:John Newlands put forward his law of octaves in 1864 in which he arranged all the elements known at the time into a table in order of relative atomic mass. When he did this, he found that each element was similar to the element eight places further on. So, the tenth element resembled the third element.

4. Which of the following can undergo sublimation? [RRB ALP & Technician Exam, 20.08.2018 Shift-III]

(1) Ammonium chlorate
(2) Ammonium sulphate
(3) Ammonium chloride
(4) Ammonium sulphide

Correct Answer: (3) Ammonium chloride

Solution:Sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase. Ammonium chloride appears to sublime upon heating but actually decomposes into ammonia and hydrogen chloride gas.

5. The number of electrons that can be accommodated in the M shell is: [RRB ALP & Technician Exam, 20.08.2018 Shift-III]

(1) 18
(2) 8
(3) 2
(4) 32

Correct Answer: (1) 18

Solution:The distribution of the electrons in the energy shells is known as electronic configuration. It is based on Bohr-Bury scheme according to which the maximum number of electrons that can be present in a particular energy shell of an atom is given by 2n², where n is the number of energy shell. The maximum electrons that can be accommodated in M shell is 18.

6. Which of the following metals reacts vigorously with cold water? [RRB ALP & Technician Exam, 20.08.2018 Shift-III]

(1) Potassium
(2) Aluminium
(3) Zinc
(4) Iron

Correct Answer: (1) Potassium

Solution:When potassium is added to water, it melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame. There is sometimes a small explosion at the end of the reaction.

7. Which of the following is used in the preparation of tincture iodine, cough syrup and many tonics? [RRB ALP & Technician Exam, 20.08.2018 Shift-III]

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

Correct Answer: (4) Ethanol

Solution:Mixture of alcohol to ethane results in the formation of ethanol and it is the active ingredient of all alcoholic drinks. Being a good solvent, it is also used in medicines like tincture of iodine, cough syrups, and many other tonics.

8. Which of the following has low resistivity? [RRB ALP & Technician Exam, 20.08.2018 Shift-III]

(1) Nichrome
(2) Glass
(3) Ebonite
(4) Diamond

Correct Answer: (1) Nichrome

Solution:

Substance	Resistivity
Glass	10¹⁴ ohm
Nichrome	10⁻⁶ ohm
Ebonite	10⁶ ohm
Diamond	10¹⁸ ohm

9. The formula C₆H₁₄ represents the hydrocarbon _______. [RRB ALP & Technician Exam, 21.08.2018 Shift-I]

(1) Hexene
(2) Hexane
(3) Hexyne
(4) Heptyne

Correct Answer: (2) Hexane

Solution:Hexane is an alkane of six carbon atoms, with the chem-ical formula C₆H₁₄ It is a chemical commonly extracted from petroleum and crude oil. It is a colorless liquid that gives off a subtle, gasoline-like odor. Hexane is highly flammable, yet it can be found in many household products such as stain removers for arts and crafts projects.

10. Which of the following solutions is the most acidic among them all? [RRB ALP & Technician Exam, 21.08.2018 Shift-I]

(1) Solution with pH value 0
(2) Solution with pH value 1
(3) Solution with pH value 6
(4) Solution with pH value 7

Correct Answer: (1) Solution with pH value 0

Solution:The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. So, a solution with pH value of 0 is most acidic. A pH greater than 7 is basic, with 14 being the most basic.