Carbon and Fossil Fuels

Petrol, alcohol, and LPG have very low ignition temperatures and are classified as inflammable (easily ignitable). Wood is combustible but has a relatively high ignition temperature and requires sustained heat to burn. Wood is not considered an inflammable substance in the strict sense.

Lignite coal has a high moisture content in the range of 45% to 55%.

Biogas is produced through anaerobic digestion of organic matter known as biomass. Biomass includes agricultural waste, animal dung, sewage, and other organic materials. Option D correctly identifies biomass as the raw material for biogas production. Options A (petrol), B (kerosene), and C (minerals) are all incorrect as they are fossil fuels or inorganic substances that cannot produce biogas through biological processes.

The luminous (yellow) zone of a flame contains unburnt carbon particles that glow due to incomplete combustion. These carbon particles are formed when hydrocarbon fuels don't fully combust due to limited oxygen supply. Option C correctly identifies the luminous zone. The blue zone (A) has complete combustion with no unburnt carbon. The dark inner zone (B) is the coolest region with unburnt fuel vapors. The non-luminous zone (D) is the blue outer zone.

Combustion is fundamentally an oxidation reaction where a substance combines with oxygen, releasing energy in the form of heat and light. Option A correctly identifies it as oxidation. Reduction (B) is the opposite process involving gain of electrons. Neutralization (C) refers to acid-base reactions. Combustion is distinctly characterized by rapid oxidation with accompanying energy release.

 The gas obtained during destructive distillation of coal is  coal gas .

Burning kerosene oil is classified as rapid combustion because it occurs at a fast rate when the fuel is ignited, producing heat and light steadily. Option A correctly identifies this as rapid combustion. Spontaneous combustion (B) occurs without external ignition. Explosion (C) involves sudden, violent combustion with pressure waves. Kerosene burning is a controlled, steady burning process, not an explosion.

LPG (liquefied petroleum gas) used as a domestic fuel has a high calorific value. The ignition temperature of this fuel is reasonably low. It is a mixture of hydrocarbons.

The cooking gas used as a fuel for domestic purposes is liquified petroleum gas.

Primary fuels or primary energy sources are dense sources of primary energy found as natural resources. Primary fuels are fuels that are found in nature and can be extracted, captured, cleaned or graded without any sort of energy conversion or transformation process.

In villages and rural areas, wood is the most commonly used naturally occurring solid fuel for cooking and heating. Option B correctly identifies wood as the primary rural solid fuel. Coal (A) is also used but less commonly in villages due to cost and availability. Paraffin (C) is a liquid fuel, not solid. Coke (D) is a processed coal product, not naturally occurring, and is less commonly used in village settings.

Anthracite is a hard, compact variety of coal that has a sub-metallic lustre. It has the highest carbon content, the fewest impurities and the highest calorific content of all types of coal. The carbon content is between 92.1% - 98% . In lignite, the carbon content is 25-35%. Bituminous contains 60-80% carbon. In peat, the carbon content is less than 60%.

Petroleum is a mixture of hydrocarbons.

Petroleum is separated into different parts by the process of fractional distillation.

Liquefied Petroleum Gas (LPG) is classified as a gaseous fuel that has been liquefied under pressure for storage and transportation. In its normal state at atmospheric pressure, LPG exists as a gas (propane and butane). Option C correctly identifies it as a gaseous fuel. Option A (solid fuel) is incorrect. Option B (liquid fuel) describes its storage form, not its fundamental classification. Option D is false as LPG is indeed a fuel.