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Gas [ Science Set 19]| UPPSC Prelims PYQ of Last 30 Years |Important Objective Question Answer, MCQ and QUIZ

1. Which of the following gas elements exist in the liquid state at room temperature?

a) Hydrogen

b) Oxygen

c) Bromine

d) Iodine

Answer. c) Bromine;

At room temperature (approximately 20°C to 25°C or 68°F to 77°F), the gas that exists in the liquid state is Bromine.

2. Mustard gas is used

a) As fuel

b) In chemical warfare

c) As a source of mustard oil

d) As decolorization

Answer. b) In chemical warfare;

Mustard gas, also known as sulfur mustard, is not used for any legitimate or legal purposes. It is a chemical warfare agent that was originally developed for military purposes. Its use is prohibited under international law by the Chemical Weapons Convention (CWC) due to its extreme toxicity and devastating effects on human health. The production, stockpiling, and use of mustard gas and other chemical weapons are considered war crimes and are illegal.

3. The methane gas-producing field is

a) Wheatfield

b) Paddy field

c) Cotton field

d) Groundnut field

Answer. b) Paddy field;

Methane gas is produced from various sources, including natural gas fields, coal mines, landfills, and agricultural activities, mainly in the Paddy field.

4.  Methane is present in the atmosphere of

a) Sun

b) Mars

c) Jupiter

d) Both b and c

Answer. b) Mars


The Sun primarily consists of hydrogen (about 74% by mass) and helium (about 24% by mass). These elements are present in the form of a hot, dense, and turbulent plasma. Other trace elements make up the remaining 2%.


Mars has a thin atmosphere composed mostly of carbon dioxide (about 95.3%). The remaining components are nitrogen (2.7%), argon (1.6%), and traces of oxygen and water vapor.


Jupiter's atmosphere is primarily composed of hydrogen (about 90-95%) and helium (about 5-10%), similar to the Sun's composition. It also contains traces of methane, ammonia, water vapor, and other compounds.


The Moon has an extremely tenuous exosphere, which means it has a near-vacuum atmosphere. It consists of very small amounts of helium, neon, hydrogen, and other trace gases. The Moon's surface does not support a significant atmosphere.

5. Consider the following statement and reason and select the correct answer with the help of the code given below: 

Assertion ( A): Ozone kills microorganisms in water.

Reason ( R): Ozone is not radioactive


a) (A) and ( R) are both correct, and (R) is the correct explanation of ( A)

b) (A) and ( R) are both correct, and (R) is not the correct explanation of ( A)

c) (A) is true, but (R) is false

d) (A) is false, but (R) is true

Answer. b) (A) and ( R) are both correct, and (R) is not the correct explanation of ( A);

Ozone (O3) gas has several important uses and applications:

Ozone Layer Protection: Ozone high in the Earth's atmosphere forms the ozone layer, which absorbs and protects us from the harmful effects of ultraviolet (UV) radiation from the sun. Ozone layer protection is crucial for preventing skin cancer, cataracts, and other health problems caused by excessive UV exposure.

Water Treatment: Ozone is a powerful disinfectant and is used in water treatment processes to purify drinking water and wastewater. It effectively kills bacteria, viruses, and other pathogens, making water safe for consumption.

Air Purification: Ozone generators are used for air purification in applications such as indoor air quality improvement and odor removal. However, its use for indoor air purification is sometimes controversial due to potential health risks associated with ozone exposure.

Medical Sterilization: Ozone is used in medical settings for sterilizing equipment and disinfecting surfaces. It is particularly useful for its ability to eliminate microorganisms and viruses.

Industrial Applications: Ozone has various industrial uses, including bleaching and disinfection in the food and beverage industry, pulp and paper processing, and as an oxidizing agent in chemical reactions.

Research: Ozone is used in laboratory and research settings for various applications, such as chemical analysis and oxidation reactions.

6. The technology used to obtain liquid oxygen or liquid hydrogen at an industrial level is called

a) Pyrotechnics

b) Pyrometry

c) Hydroponics

d) Cryogenics

Answer. d) Cryogenics;

Pyrotechnics: Pyrotechnics is the science and art of creating fireworks, explosives, and various types of fireworks displays. It involves the controlled combustion of materials to produce light, heat, sound, smoke, or other effects for entertainment, celebrations, and military purposes.

Pyrometry: Pyrometry is the measurement of high temperatures, typically using specialized instruments and techniques. It is important in fields like materials science, metallurgy, and industrial processes where accurate temperature measurement is crucial.

Hydroponics: Hydroponics is a method of growing plants without soil. Instead, plants are grown in nutrient-rich water solutions or inert growing mediums. Hydroponics allows for precise control over environmental factors like nutrient levels, pH, and temperature, making it an efficient way to cultivate crops.

Cryogenics: Cryogenics is the branch of physics and engineering that deals with extremely low temperatures. It involves the study of materials and phenomena at temperatures well below those of typical refrigeration or cooling systems. Cryogenic applications include the storage and transportation of liquefied gases like liquid nitrogen and the study of superconductivity at low temperatures.

7. The gases used in the breathing activity of divers are

a) Oxygen and Nitrogen

b) Oxygen and helium

c) Oxygen and Organ

d) Oxygen and Neon

Answer. b) Oxygen and helium;

8. Easily soluble in water

a) Carbon

b) Nitrogen

c) Ammonia

d) Iodine

Answer. c) Ammonia;

Among the options you provided, ammonia (NH3) is easily soluble in water. Ammonia readily dissolves in water to form ammonium hydroxide (NH4OH), creating an alkaline solution. It is highly soluble due to its ability to form hydrogen bonds with water molecules, making it a polar molecule that interacts well with polar water molecules.

Carbon (C) is not soluble in water, and nitrogen (N2) is also not significantly soluble in water under normal conditions. Iodide typically refers to iodide ions (I-), and they are soluble in water, although their solubility may vary depending on the specific compound.

9. Which is used as Laughing Gas

a) Nitrous oxide

b) Nitrogen dioxide

c) Nitrogen trioxide

d) Nitrogen tetraoxide

Answer. a) Nitrous oxide;

"Laughing gas" is a common colloquial term for nitrous oxide (N2O), which is a colorless, sweet-smelling gas. It earned this nickname because inhaling nitrous oxide can cause euphoria and laughter in some individuals.

10. Which one of the following is not correct?

a) Bordeaux mixture is a mixture of copper sulfate and calcium Hydroxide in water and is used as a fungicide.

b) Boric acid is used in the pharmaceutical industry and also as a food preservative

c) Dry ice is solid carbon dioxide

d) Nitric oxide is a laughing gas

Answer. d) Nitric oxide is a laughing gas

The gas used to inflate the tires of an aircraft is typically nitrogen (N2). Aircraft tires are filled with nitrogen instead of regular air (which contains oxygen) for several reasons:

Stability: Nitrogen is a dry and inert gas, which means it doesn't contain moisture or reactive components like oxygen. This helps to maintain more stable tire pressure, especially at high altitudes and during temperature fluctuations, which is crucial for aircraft safety.

Reduced Fire Risk: Nitrogen reduces the risk of tire fires. When an aircraft lands, the tires can become very hot due to the friction of landing. If the tires contain oxygen, there is a higher risk of a tire fire. Nitrogen, being inert, doesn't support combustion.

Preventing Corrosion: Oxygen in regular air can contribute to corrosion and oxidation of tire components over time. Nitrogen helps reduce these effects, prolonging the life of the tires.

11. Discharge of Nitrogen causes

a) Increase in the amount of atmospheric nitrogen

b) Increase in the amount of nitrogen in the lithosphere and in the atmosphere unchanged 

c) The amount of nitrogen in the lithosphere and in the atmosphere is unchanged

d) Destructive of Nitrifying bacteria

Answer. c) The amount of nitrogen in the lithosphere and in the atmosphere is unchanged

12. The Gas used to inflate the Tyres of an aircraft is

a) Hydrogen

b) Nitrogen

c) Helium

d) Neon

Answer. b) Nitrogen

13. Helium is preferred to Hydrogen in air balloons because it

a) Is cheaper

b) Is less dense

c) Has greater lifting power

d) Does not form an explosive mixture with air

Answer. d) Does not form an explosive mixture with air;

Helium is preferred over hydrogen in air balloons primarily because it is non-flammable and safer. Here are the main reasons why helium is used instead of hydrogen:

Non-Flammable: Helium is an inert, non-flammable gas, which means it does not burn or support combustion. In contrast, hydrogen is highly flammable and can easily ignite, posing a significant fire hazard.

Safety: The use of hydrogen in the early days of aviation and ballooning led to several tragic accidents due to its flammability. Replacing hydrogen with helium significantly improved the safety of air travel and ballooning.

Stability: Helium provides more stable and predictable buoyancy than hydrogen. Its lifting capacity is not affected by variations in temperature or atmospheric conditions to the same extent as hydrogen.

Environmental Considerations: Helium is also environmentally friendly and does not pose the same environmental risks as hydrogen, which can contribute to ozone layer depletion when released into the atmosphere.


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