Chemistry (Part-X)

Total Questions: 50

31. Which of the following minerals produces green colour in fireworks? [S.S.C. Online Graduate Level (T-I) 20.08.2021 (Shift-I) ]

(a) Zinc
(b) Barium
(c) Copper
(d) Sodium

Correct Answer: (b) Barium

Solution:Barium chloride, a salt of barium (Ba), is used for the production of green light in fireworks and firecrackers. Apart from this, sodium nitrate is used to produce yellow color and copper chloride is used to produce the blue color.

32. Using which of the following processes can one separate a solute from its solution? [S.S.C. Online CHSL (T-I) 11.01.2017 (Shift-II) ]

(a) Sedimentation
(b) Evaporation
(c) Filtration
(d) Condensation

Correct Answer: (b) Evaporation

Solution:Evaporation is the process of heating a solution to drive off the solvent (e.g., water), leaving the solid solute behind. This is a common method for separating a non-volatile solute from a volatile solvent.

(a) Sedimentation: Separates insoluble solids from liquids by gravity.
(c) Filtration: Separates insoluble solids from liquids using a filter.
(d) Condensation: Changes a gas into a liquid.

33. Which of the following is a chemical change? [S.S.C. JE Mechanical Exam 22.03.2021 (Shift-II) ]

(a) Boiling of milk
(b) Burning of wood
(c) Crushing of a can
(d) Expansion of substance on heating

Correct Answer: (b) Burning of wood

Solution:A chemical change results in the formation of new substances with different chemical properties.

Burning of wood: Wood reacts with oxygen to produce ash, carbon dioxide, water vapor, and other gases. This is an irreversible change where new compounds are formed.

Boiling of milk: A physical change where water turns into vapor, but the milk's chemical composition largely remains milk.

Crushing of a can: A physical change where the shape changes, but the material (e.g., aluminum) remains chemically the same.

Expansion of substance on heating: A physical change in volume, not in chemical composition.

34. Which of the following is NOT advisable as a process of separation of components of a mixture? [S.S.C. JE Mechanical Exam 22.03.2021 (Shift-II) ]

(a) Winnowing
(b) Filtration
(c) Decantation
(d) Sedimentation

Correct Answer: (a) Winnowing

Solution:Winnowing is a method used to separate lighter particles from heavier ones by using wind or air currents. It's commonly used for separating grain from chaff. While it's effective for mixtures with significant differences in density, it wouldn't be suitable for mixtures where the components have similar densities or are very fine. For example, winnowing wouldn't be effective in separating sand from fine dust.

35. In arc welding, Argon is used because of its— [S.S.C. Online Graduate Level (T-I) 1.09.2016 (Shift-II) ]

(a) Low reactivity with metal
(b) Ability to lower the melting point of the metal
(c) High flammability
(d) High calorific value

Correct Answer: (a) Low reactivity with metal

Solution:Argon is an inert (noble) gas. In arc welding (specifically Gas Metal Arc Welding - GMAW or Gas Tungsten Arc Welding - GTAW), argon is used as a shielding gas. Its low reactivity with metal prevents atmospheric gases like oxygen and nitrogen from reacting with the hot molten metal, which would lead to oxidation, porosity, and embrittlement of the weld. This ensures a clean and strong weld.

36. Which among the following is used to generate light to weld metals? [S.S.C. Online CHSL (T-I) 15.01.2017 (Shift-I) ]

(a) Ethylene
(b) Acetylene
(c) Glycol
(d) Oxalic Acid
C₂H₂

Correct Answer: (b) Acetylene

Solution:Acetylene (C₂H₂) is widely used in oxy-acetylene welding. When combusted with oxygen, it produces a very hot flame (up to 3,500 °C or 6,330 °F) and a bright light, which is used to melt and join metals.

37. Inert gases are— [S.S.C. Online Graduate Level (T-I) 1.09.2016 (Shift-II) ]

(a) Miscible with water
(b) Not stable
(c) Chemically unreactive
(d) Chemically very active

Correct Answer: (c) Chemically unreactive

Solution:Inert gases (also known as noble gases) are elements in Group 18 of the periodic table (Helium, Neon, Argon, Krypton, Xenon, Radon). Their outer electron shells are full, making them exceptionally stable and therefore chemically unreactive under normal conditions.

38. Which among the following is a cation? [S.S.C. Online Graduate Level (T-I) 7.03.2020 (Shift-I) ]

(a) Ammonium
(b) Fluoride
(c) Chloride
(d) Iodide

Correct Answer: (a) Ammonium

Solution:Ammonium (NH₄⁺) is a cation, while fluoride (F⁻), chloride (CH⁻), and iodide (I⁻) are anions of halogens (group 17 elements).

39. Which one of the following statements is incorrect. [S.S.C. Online Graduate Level (T-I) 7.03.2020 (Shift-II) ]

(a) Matter is made up of small particles.
(b) Evaporation causes cooling.
(c) Brass is a mixture of 30% Zinc and 70% Copper.
(d) The measurable unit of pressure is denoted in Metre.

Correct Answer: (d) The measurable unit of pressure is denoted in Metre.

Solution:(a) Matter is made up of small particles: Correct. This is a fundamental concept of matter (atoms, molecules).

(b) Evaporation causes cooling: Correct. When liquid evaporates, it takes heat from its surroundings, leading to a cooling effect.

(c) Brass is a mixture of 30% Zinc and 70% Copper: Correct. Brass is an alloy (a mixture) of copper and zinc, with typical compositions varying but often around 70% copper and 30% zinc.

(d) The measurable unit of pressure is denoted in Metre: Incorrect. Metre is a unit of length. Pressure is measured in units like Pascal (Pa), pounds per square inch (psi), atmosphere (atm), or millimeters of mercury (mmHg).

40. Name the densest stable element known on earth. [S.S.C. Online Graduate Level (T-I) 7.03.2020 (Shift-III) ]

(a) Tungsten
(b) Osmium
(c) Aluminium
(d) Rhodium

Correct Answer: (b) Osmium

Solution:Osmium (Os) is generally considered the densest stable naturally occurring element known on Earth, with a density of

22.59 g / c m³

. Iridium is very close. Tungsten is also very dense but less so than osmium.

(a) Tungsten: Very dense but less than osmium.
(c) Aluminium: Much less dense.
(d) Rhodium: Dense, but less than osmium.

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