0
0

Fuels and Combustion

Introduction

The topic "Fuels and Combustion" is fundamental in General Science and frequently appears in exams like SSC CGL, RRB NTPC, and IBPS PO. Understanding the types of fuels, their properties, and the combustion process is essential for solving questions related to energy sources, chemical reactions, and environmental impact.

Pattern: Fuels and Combustion

Pattern

This pattern tests knowledge of different types of fuels, their combustion reactions, and related concepts such as calorific value and pollution.

Key Concept:

Combustion is a chemical reaction between a fuel and oxygen that produces heat and light.

Important Points:

  • Fuels = Substances that release energy on burning (e.g., coal, petrol, LPG, wood)
  • Types of Fuels = Solid (coal, wood), Liquid (petrol, diesel), Gas (LPG, natural gas)
  • Complete Combustion = Fuel burns in sufficient oxygen producing CO₂ and H₂O
  • Incomplete Combustion = Insufficient oxygen leads to CO and soot formation
  • Calorific Value = Amount of heat energy released on complete combustion of unit mass of fuel (unit: kJ/kg)

Related Topics:

  • Energy sources and conservation
  • Air pollution and its control
  • Chemical reactions and balancing equations

Step-by-Step Example

Question

Which of the following is a gaseous fuel commonly used for domestic cooking?

Options:

  • A. Coal
  • B. Petrol
  • C. Liquefied Petroleum Gas (LPG)
  • D. Diesel

Solution

  1. Step 1: Identify fuel types

    Coal is a solid fuel, petrol and diesel are liquid fuels, LPG is a gaseous fuel.

  2. Step 2: Match fuel to domestic cooking use

    LPG is widely used as a clean gaseous fuel for cooking in households.

  3. Step 3: Confirm other options

    Coal is solid and not commonly used for domestic cooking; petrol and diesel are fuels for engines, not cooking.

  4. Final Answer:

    Liquefied Petroleum Gas (LPG) → Option C

  5. Quick Check:

    Common domestic gaseous fuel = LPG ✅

Quick Variations

This pattern may appear as questions on types of fuels, products of combustion, calorific values, or environmental effects of burning fuels.

Trick to Always Use

  • Remember: "Gas for cooking = LPG" to quickly identify gaseous fuel questions.
  • Mnemonic for combustion products: Complete Combustion → CO₂ + H₂O; Incomplete → CO + soot.

Summary

Summary

  • Fuels release energy by combustion with oxygen.
  • Types of fuels: solid, liquid, and gaseous.
  • Complete combustion produces carbon dioxide and water; incomplete produces carbon monoxide and soot.

Remember:
“Fuel + Oxygen → Heat + Light; Complete = CO₂ + H₂O”

Practice

(1/5)
1. Which of the following is a solid fuel commonly used in households for cooking and heating?
easy
A. Coal
B. Petrol
C. LPG
D. Natural Gas

Solution

  1. Step 1: Identify fuel types

    Coal is a solid fuel, petrol is a liquid fuel, LPG and natural gas are gaseous fuels.

  2. Step 2: Match fuel to household use

    Coal is traditionally used as a solid fuel for cooking and heating in many households.

  3. Final Answer:

    Coal → Option A

  4. Quick Check:

    Solid household fuel = Coal ✅
Hint: Solid fuel for heating and cooking = Coal
Common Mistakes: Confusing petrol or LPG as solid fuels instead of coal.
2. What is the main product formed during complete combustion of a hydrocarbon fuel?
easy
A. Carbon monoxide and water
B. Soot and carbon dioxide
C. Carbon dioxide and water
D. Hydrogen and oxygen

Solution

  1. Step 1: Understand combustion products

    Complete combustion occurs when fuel burns in sufficient oxygen producing carbon dioxide and water.

  2. Step 2: Eliminate incorrect products

    Carbon monoxide and soot are products of incomplete combustion, hydrogen and oxygen are not combustion products.

  3. Final Answer:

    Carbon dioxide and water → Option C

  4. Quick Check:

    Complete combustion products = Carbon dioxide and water ✅
Hint: Complete combustion → CO₂ + H₂O
Common Mistakes: Confusing incomplete combustion products (CO, soot) with complete combustion.
3. Which of the following fuels is considered the cleanest fuel due to absence of carbon in its combustion?
easy
A. Coal
B. Petrol
C. LPG
D. Hydrogen

Solution

  1. Step 1: Understand clean fuel concept

    A clean fuel produces minimal or no pollutants like carbon dioxide, carbon monoxide, or soot during combustion.

  2. Step 2: Analyze fuel composition

    Hydrogen contains no carbon, so its combustion produces only water vapour.

  3. Step 3: Eliminate other fuels

    Coal, petrol, and LPG contain carbon and release carbon dioxide on burning.

  4. Final Answer:

    Hydrogen → Option D

  5. Quick Check:

    Cleanest fuel (no carbon) = Hydrogen ✅
Hint: No carbon in fuel → Clean combustion → Hydrogen
Common Mistakes: Assuming LPG is the cleanest fuel without considering carbon content.
4. Incomplete combustion of a hydrocarbon fuel mainly produces which harmful gas?
medium
A. Carbon dioxide
B. Oxygen
C. Nitrogen
D. Carbon monoxide

Solution

  1. Step 1: Identify incomplete combustion products

    Incomplete combustion occurs when oxygen supply is insufficient, producing carbon monoxide and soot.

  2. Step 2: Recognize harmful gas

    Carbon monoxide is a poisonous gas harmful to humans, unlike carbon dioxide or nitrogen.

  3. Final Answer:

    Carbon monoxide → Option D

  4. Quick Check:

    Incomplete combustion harmful gas = Carbon monoxide ✅
Hint: Incomplete combustion → Carbon monoxide + soot
Common Mistakes: Confusing carbon dioxide as harmful gas from incomplete combustion.
5. Which of the following is NOT a characteristic of a good fuel?
medium
A. Produces large amount of smoke
B. Easy to ignite
C. High calorific value
D. Burns without leaving residue

Solution

  1. Step 1: Understand characteristics of good fuel

    Good fuels have high calorific value, ignite easily, and burn cleanly without much smoke or residue.

  2. Step 2: Identify incorrect characteristic

    Producing large amounts of smoke indicates incomplete combustion and pollution, which is undesirable.

  3. Final Answer:

    Produces large amount of smoke → Option A

  4. Quick Check:

    Good fuel characteristic = Burns cleanly without smoke ✅
Hint: Good fuel = High energy + Clean burning
Common Mistakes: Mistaking smoke production as a sign of good fuel.

Mock Test

Ready for a challenge?

Take a 10-minute AI-powered test with 10 questions (Easy-Medium-Hard mix) and get instant SWOT analysis of your performance!

10 Questions
5 Minutes