The Fuel

1. Which one of the following substances does not belong to class ‘B’ fir

Which one of the following substances does not belong to class ‘B’ fire ?

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Molten Sulphur
Alcohol
Solvent
Paint
This question was previously asked in
UPSC CISF-AC-EXE – 2020
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Paint is the substance among the options that does not exclusively belong to Class ‘B’ fires, as it can also cause Class ‘A’ fires (e.g., dried paint) or be non-flammable (water-based paint).
– Class B fires involve flammable liquids and gases (e.g., petrol, oil, alcohol, propane).
– Alcohol and Solvents are standard examples of flammable liquids that cause Class B fires.
– Molten Sulphur, while solid at room temperature, burns as a flammable liquid when molten and is classified as a Class B fire hazard.
– Paint’s classification depends on its composition. Solvent-based paints cause Class B fires due to the flammable solvents. However, water-based paints contain minimal flammable solvents; their fire risk is primarily from the combustible solid components/residue, which would be a Class A fire. Dried paint is also a combustible solid (Class A).
Fire classification systems categorize fires based on the type of fuel involved, as different types of fires require different extinguishing agents. While many paints are Class B due to solvents, the general term ‘Paint’ is ambiguous and can include substances that result in Class A fires, making it the one least definitively belonging *only* to Class B among the options.

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2. What is a fire triangle ?

What is a fire triangle ?

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Combination of Oxygen, Fuel and Heat
Combination of Heat, Gas and CO₂
Combination of Fuel, CO₂ and Heat
None of the above
This question was previously asked in
UPSC CISF-AC-EXE – 2017
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The correct answer is A) Combination of Oxygen, Fuel and Heat.
The fire triangle is a simple model illustrating the three elements necessary for most fires to ignite and continue to burn: Fuel (something to burn), Oxygen (a supply of oxidizer, usually air), and Heat (sufficient to raise the fuel to its ignition temperature). Removing any one of these elements can extinguish the fire.
A more complex model, the fire tetrahedron, adds a fourth element: a chemical chain reaction. This is particularly relevant for understanding how certain extinguishing agents (like halons) work by interrupting this reaction. However, the fundamental fire triangle remains a widely used and accurate model for basic understanding.

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3. Which one of the following is the exhaust pipe emission from Fuel Cell

Which one of the following is the exhaust pipe emission from Fuel Cell Electric Vehicles, powered by hydrogen ?

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Hydrogen peroxide
Hydronium
Oxygen
Water vapour
This question was previously asked in
UPSC IAS – 2024
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Fuel Cell Electric Vehicles (FCEVs) powered by hydrogen generate electricity through an electrochemical process where hydrogen reacts with oxygen from the air. The primary chemical reaction in a hydrogen fuel cell is 2H₂ + O₂ → 2H₂O. This reaction produces water (H₂O) and energy (electricity and heat). The water produced is expelled from the vehicle, typically as water vapour, which is essentially steam.
The fundamental output of a hydrogen fuel cell, besides electricity and heat, is water.
FCEVs are considered zero-emission vehicles at the point of use because their only tailpipe emission is water vapour, unlike internal combustion engines that emit various pollutants and greenhouse gases. The environmental impact of hydrogen fuel cell technology depends significantly on how the hydrogen fuel itself is produced (e.g., from renewable sources or fossil fuels).

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4. Natural gas is a mixture of gases and contains mainly

Natural gas is a mixture of gases and contains mainly

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methane and higher hydro-carbons
butane and isobutene
methane only
methane, hydrogen and carbon monoxide
This question was previously asked in
UPSC CAPF – 2013
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Natural gas is a naturally occurring hydrocarbon gas mixture. The primary component of natural gas is methane (CH₄), which is the simplest hydrocarbon molecule. However, natural gas is typically not pure methane. It also contains varying amounts of other, heavier gaseous hydrocarbons such as ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀), and pentane (C₅H₁₂), commonly referred to as higher hydrocarbons or natural gas liquids (NGLs). In addition to hydrocarbons, natural gas can contain non-hydrocarbon gases such as carbon dioxide (CO₂), nitrogen (N₂), hydrogen sulfide (H₂S), and trace amounts of other gases like helium. The question asks for the main components. While methane is the most abundant component, “methane and higher hydro-carbons” accurately describes the primary composition.
Natural gas is a mixture, predominantly methane, but also containing other light hydrocarbons.
The exact composition of natural gas varies depending on the source (gas field). Raw natural gas must be processed to remove impurities and heavier hydrocarbons before it can be distributed and used as fuel. The higher hydrocarbons are often separated and sold as valuable byproducts (NGLs).

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5. Which one of the following is the major constituent of biogas ?

Which one of the following is the major constituent of biogas ?

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Carbon dioxide
Nitrous oxide
Methane
Oxygen
This question was previously asked in
UPSC NDA-2 – 2019
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The correct option is C) Methane.
Biogas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen, primarily consisting of methane and carbon dioxide.
The typical composition of biogas is about 50-75% methane (CH4) and 25-50% carbon dioxide (CO2), with traces of other gases like hydrogen sulfide, nitrogen, and hydrogen. Methane is the primary combustible component that gives biogas its fuel value.

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6. Which one of the following is called ‘syngas’?

Which one of the following is called ‘syngas’?

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C(s) + H₂O(g)
CO(g) + H₂O(g)
CO(g) + H₂(g)
NO₂(g) + H₂(g)
This question was previously asked in
UPSC NDA-2 – 2018
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‘Syngas’ is a mixture of carbon monoxide (CO) and hydrogen (H₂).
– Syngas, or synthesis gas, is a fuel gas consisting primarily of carbon monoxide (CO) and hydrogen (H₂).
– It is produced through processes like gasification of coal, biomass, or waste, or steam reforming of natural gas.
– Syngas is a crucial intermediate in the production of synthetic fuels, ammonia, methanol, and other chemicals.
Option A, C(s) + H₂O(g), represents a reaction (steam-carbon reaction or gasification) used to produce syngas. Option B, CO(g) + H₂O(g), represents reactants in the water-gas shift reaction, which can be used to adjust the CO:H₂ ratio in syngas. Option D is a mix of nitrogen dioxide and hydrogen, which is not syngas.

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7. The LPG cooking gas contains propane and butane as the constituents. A

The LPG cooking gas contains propane and butane as the constituents. A sulfur containing compound is added to the LPG, because

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it lowers the cost of production
it enhances the efficiency of LPG
it facilitates easy detection of leakage of the gas
it assists in liquefying hydrocarbons
This question was previously asked in
UPSC NDA-2 – 2016
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The addition of a sulfur-containing compound to LPG cooking gas facilitates the easy detection of leakage.
LPG (Liquefied Petroleum Gas), which primarily consists of propane and butane, is naturally odorless. Leaked gas can accumulate and pose a significant fire and explosion hazard if not detected. To ensure safety, a strong-smelling substance, usually a volatile organic sulfur compound like ethyl mercaptan (ethanethiol), is added as an odorant. This allows even small leaks to be detected by smell, prompting corrective action before a dangerous concentration of gas builds up.
The amount of odorant added is very small, typically only a few parts per million, which is sufficient to make the gas detectable by the human nose at concentrations well below the flammability limit. The odorant does not affect the combustion properties or efficiency of the LPG.

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8. Consider the following reaction: CH₄(g) + H₂O(g) 1270 K CO(g) + 3

Consider the following reaction:
CH₄(g) + H₂O(g)

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1270 K

CO(g) + 3H₂(g)
In the reaction given above, the mixture of CO and H₂, is:

natural gas
water gas
producer gas
industrial gas
This question was previously asked in
UPSC NDA-2 – 2015
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The correct answer is B. The mixture of CO and H₂ produced by the steam reforming of methane is known as water gas.
– The reaction CH₄(g) + H₂O(g) → CO(g) + 3H₂(g) is called steam reforming of methane.
– The resulting mixture of carbon monoxide (CO) and hydrogen (H₂) is commonly referred to as synthesis gas or, specifically when produced via steam reactions with carbonaceous materials or hydrocarbons, water gas.
– Producer gas is formed by reacting carbonaceous fuel with air and steam, containing CO, H₂, N₂, and CO₂.
– Natural gas is primarily methane.
Water gas and synthesis gas are important industrial feedstocks used in the production of various chemicals, including methanol, ammonia, and synthetic fuels (via the Fischer-Tropsch process).

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9. Water gas is a mixture of:

Water gas is a mixture of:

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CO₂ and H₂
CO and H₂
CO₂ and H₂O
CO and H₂O
This question was previously asked in
UPSC NDA-1 – 2024
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Water gas is a mixture of carbon monoxide (CO) and hydrogen (H₂).
It is produced by passing steam over red-hot carbon (like coke or coal) at high temperatures (typically 800-1000°C). The reaction is: H₂O(g) + C(s) → CO(g) + H₂(g).
Water gas is a significant industrial fuel and a source of hydrogen. It is also known as synthesis gas or syngas when the ratio of CO to H₂ is adjusted, as it is used in the synthesis of various organic compounds.

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10. Which one of the following is an example of a clean fuel ?

Which one of the following is an example of a clean fuel ?

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Coke
Propane
Petrol
Wax
This question was previously asked in
UPSC NDA-1 – 2019
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Propane is an example of a clean fuel among the given options.
Clean fuels produce less pollution when burned compared to conventional fuels. Propane, being a gaseous fuel (part of LPG – Liquefied Petroleum Gas), generally burns more cleanly than solid fuels like coke or liquid fuels like petrol and wax, which produce significant amounts of smoke, particulate matter, and other pollutants like sulfur oxides and nitrogen oxides. While no fuel is perfectly “clean,” propane is significantly cleaner than the other options listed in terms of common air pollutants.
Common examples of cleaner fuels include natural gas (methane), LPG (propane and butane), hydrogen, and biofuels like ethanol and biodiesel (though the ‘cleanliness’ of biofuels is debated depending on production). Coke is a solid fuel derived from coal, primarily carbon, and its combustion produces significant air pollution. Petrol (gasoline) is a complex mix of hydrocarbons used in internal combustion engines and is a major source of air pollution. Wax is a solid hydrocarbon often used in candles or as fuel, producing smoke and particulates when burned.

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