Sulphur, Nitrogen, Halogen, Inert Gases

1. The original copies of the Constitution of India are kept in the Parli

The original copies of the Constitution of India are kept in the Parliament library in cases filled with which one of the following inert gases?

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Helium
Nitrogen
Argon
Hydrogen
This question was previously asked in
UPSC Combined Section Officer – 2021-22
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The correct answer is A, Helium.
The original handwritten copies of the Constitution of India are preserved in the Parliament Library in New Delhi. They are stored in special cases filled with Helium gas to prevent degradation due to oxidation and humidity. Helium is a noble gas and is inert, making it ideal for long-term preservation of such valuable documents.
Besides the Constitution, original manuscripts of other important documents and books are also preserved using similar techniques in libraries and archives worldwide. The practice ensures that these historical documents remain intact for future generations.

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2. Chips bags contain which gas ?

Chips bags contain which gas ?

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Oxygen
Hydrogen
Carbon dioxide
Nitrogen
This question was previously asked in
UPSC CISF-AC-EXE – 2021
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Chips bags are filled with nitrogen gas. Nitrogen is an inert gas that helps prevent oxidation of the chips, which causes them to become stale and rancid. It also provides cushioning, protecting the fragile chips from breaking during transport and handling.
Nitrogen gas is inert, meaning it does not react readily with the food.
Oxygen would react with the fats in the chips, causing rancidity.
The gas also helps maintain the structural integrity of the chips.
This process of flushing food packaging with an inert gas is called Modified Atmosphere Packaging (MAP) and is commonly used for various food products to extend shelf life.

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3. Which one of the following gases produces a red light when electricity

Which one of the following gases produces a red light when electricity flows through it ?

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Helium
Argon
Nitrogen
Neon
This question was previously asked in
UPSC CAPF – 2020
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Neon gas produces a red light when electricity flows through it.
When an electric current passes through a low-pressure gas in a tube, the gas atoms are excited and emit light as they return to their ground state. Different gases emit light of characteristic wavelengths (colors). Neon gas specifically emits a bright reddish-orange light when used in discharge tubes, famously known as “neon signs.”
Helium typically emits a white, yellowish, or pinkish-orange light. Argon typically emits blue or violet light. Nitrogen can emit pink, orange, or yellow light depending on conditions. Other colors in commercial “neon signs” are often achieved by using different noble gases (like argon for blue) or by coating the inside of the tube with phosphors that fluoresce different colors when excited by the ultraviolet light emitted by gases like mercury vapor or argon.

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4. In some parts of India, consumption of underground water causes mottle

In some parts of India, consumption of underground water causes mottled teeth and bone damage. Which one of the following is responsible for this malady ?

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Fluoride ion
Chloride ion
Oxide ion
Carbonate ion
This question was previously asked in
UPSC CAPF – 2009
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Fluoride ion is responsible for mottled teeth and bone damage caused by consuming contaminated underground water in some parts of India.
Excessive intake of fluoride, primarily through drinking water, leads to a condition called fluorosis. Dental fluorosis causes discoloration and mottling of tooth enamel, especially during tooth development. Skeletal fluorosis affects bones, causing joint pain, stiffness, and in severe cases, crippling deformities. Many areas in India have groundwater naturally high in fluoride.
While fluoride is essential for strengthening teeth enamel in appropriate amounts, its excess can be harmful. Chloride, Oxide, and Carbonate ions are common in water but are not the primary cause of mottled teeth and bone damage in the way that excess fluoride is.

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5. The mass of 0.5 mole of N₂ gas is

The mass of 0.5 mole of N₂ gas is

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7 g
14 g
21 g
28 g
This question was previously asked in
UPSC NDA-2 – 2024
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The correct answer is B) 14 g.
The mass of a substance can be calculated using the number of moles and its molar mass. The formula is: Mass = Number of moles × Molar mass.
Nitrogen gas is diatomic, represented as N₂. The atomic mass of Nitrogen (N) is approximately 14 g/mol. Therefore, the molar mass of N₂ gas is 2 × 14 g/mol = 28 g/mol.
Given the number of moles is 0.5 mole, the mass of 0.5 mole of N₂ gas is 0.5 mol × 28 g/mol = 14 g.
A mole is a unit of amount of substance, defined as containing Avogadro’s number (approximately 6.022 × 10²³) of elementary entities (atoms, molecules, ions, etc.). The molar mass of a substance is the mass of one mole of that substance.

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6. To help deep-sea divers breathe, they carry cylinders of oxygen mixed

To help deep-sea divers breathe, they carry cylinders of oxygen mixed with

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chlorine
helium
nitrogen
ozone
This question was previously asked in
UPSC NDA-2 – 2022
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To help deep-sea divers breathe, they carry cylinders of oxygen mixed with helium.
At high pressures experienced during deep-sea dives, the nitrogen in air can cause nitrogen narcosis, which impairs judgment and coordination. Oxygen at high partial pressures can also become toxic. To avoid these issues, the breathing gas mixture often replaces nitrogen with helium, which is less narcotic and also less dense than nitrogen, making breathing easier at depth. This mixture of oxygen and helium is called Heliox.
Other gas mixtures like Trimix (oxygen, helium, and nitrogen) are also used depending on the depth and duration of the dive. Chlorine and ozone are toxic gases and would not be used in breathing mixtures.

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7. Which one of the following statements regarding Bleaching powder and D

Which one of the following statements regarding Bleaching powder and D.D.T. is correct ?

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Both are inorganic compounds
Both are organic compounds
Both contain chlorine
Both contain calcium
This question was previously asked in
UPSC NDA-2 – 2020
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The correct answer is (C) Both contain chlorine.
Let’s look at the chemical composition of both substances:
– Bleaching powder is Calcium oxychloride (CaOCl2). It is an inorganic compound containing calcium and chlorine.
– D.D.T. is Dichloro-diphenyl-trichloroethane ((ClC6H4)2CH(CCl3)). It is an organic compound (containing carbon and hydrogen, with chlorine substituents) containing chlorine but no calcium.
Comparing the options:
A) Both are inorganic compounds: False (DDT is organic).
B) Both are organic compounds: False (Bleaching powder is inorganic).
C) Both contain chlorine: True (Bleaching powder has chlorine, and DDT has multiple chlorine atoms).
D) Both contain calcium: False (DDT does not contain calcium).
Bleaching powder is used as a bleaching agent and disinfectant. DDT was a widely used insecticide but is now banned or restricted in many countries due to its environmental persistence and harmful effects.

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8. The principal use of hydrofluoric acid is

The principal use of hydrofluoric acid is

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in etching glass
as a bleaching agent
as an extremely strong oxidizing agent
in the preparation of strong organic fluorine compounds
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UPSC NDA-2 – 2017
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The principal use of hydrofluoric acid is related to its unique property of reacting with silicon dioxide (silica).
Hydrofluoric acid (HF) is highly corrosive and capable of dissolving many materials, particularly oxides and silicates. Its ability to react with SiO₂, the main component of glass, allows it to etch glass surfaces. This reaction is: SiO₂ + 4HF → SiF₄ + 2H₂O. This property is exploited extensively in industries for etching glass, cleaning silicon wafers in electronics, and polishing metals.
While HF is used in the production of organic fluorine compounds, as a catalyst, and in other chemical processes, etching glass and processing silicon are widely cited as principal or distinctive uses due to its unique reactivity with silicates. It is not primarily a bleaching agent or an extremely strong oxidizing agent.

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9. Identify the element having zero valency

Identify the element having zero valency

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Sulphur
Phosphorous
Lead
Radon
This question was previously asked in
UPSC NDA-2 – 2016
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Valency is the combining capacity of an element. Elements with zero valency are those that are chemically inert and do not readily form chemical bonds under normal conditions because their outermost electron shell is full. These elements are the noble gases. Among the given options, Radon (Rn) is a noble gas.
– Sulphur (S) typically has valencies of 2, 4, or 6.
– Phosphorous (P) typically has valencies of 3 or 5.
– Lead (Pb) typically has valencies of 2 or 4.
– Radon (Rn) is a noble gas (Group 18 of the periodic table) and its valency is considered zero.
Noble gases (Helium, Neon, Argon, Krypton, Xenon, and Radon) have a stable electron configuration with a full outermost electron shell (except Helium, which has 2 electrons in its single shell), making them very unreactive.

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10. Which among the following is the correct arrangement of halogens in th

Which among the following is the correct arrangement of halogens in the increasing order of their oxidizing nature ?

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F, Cl, Br, I
Cl, Br, F, I
Br, I, Cl, F
I, Br, Cl, F
This question was previously asked in
UPSC NDA-1 – 2023
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The oxidizing nature of an element refers to its ability to gain electrons and cause the oxidation of another substance. For halogens (Group 17 elements: F, Cl, Br, I, At), the oxidizing power generally decreases down the group. This is because electronegativity and electron affinity decrease, while the atomic radius increases, making it less favorable to gain an electron as you move from Fluorine to Iodine. Therefore, the increasing order of their oxidizing nature is Iodine (I) < Bromine (Br) < Chlorine (Cl) < Fluorine (F). Fluorine is the strongest oxidizing agent among the halogens.
– Oxidizing nature is the ability to gain electrons.
– For halogens, oxidizing power decreases down the group (from F to I).
– This is due to decreasing electronegativity and electron affinity.
– The order of oxidizing strength is F₂ > Cl₂ > Br₂ > I₂.
– The increasing order of oxidizing nature is I < Br < Cl < F.
Fluorine is the most electronegative element and has a very high oxidizing potential. It can oxidize all other halide ions. Chlorine can oxidize bromide and iodide ions. Bromine can oxidize iodide ions, but not fluoride or chloride ions. Iodine is the weakest oxidizing agent among the common halogens.

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