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Combustion and Flame - Harmful Effects of Burning Fuels

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Unburnt Carbon Particles: Carbon fuels like wood, coal, and petroleum release unburnt carbon particles (CC). These fine particles are dangerous pollutants causing respiratory diseases such as asthma.

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Incomplete Combustion: When fuels are burnt in insufficient oxygen, they produce Carbon Monoxide (COCO), a highly poisonous gas. Sleeping in a closed room with burning coal is dangerous because COCO can kill persons sleeping in that room.

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Global Warming: Combustion of most fuels releases Carbon Dioxide (CO2CO_2) into the environment. Increased concentration of CO2CO_2 in the air is believed to cause global warming (the rise in temperature of the atmosphere of the earth).

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Acid Rain: Burning of coal and diesel releases Sulphur Dioxide (SO2SO_2). Nitrogen oxides (NOxNO_x) are given off by petrol engines. These oxides dissolve in rain water to form acids. Such rain is called Acid Rain, which is very harmful for crops, buildings, and soil.

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Marble Cancer: Acid rain reacts with the calcium carbonate (CaCO3CaCO_3) of monuments like the Taj Mahal, causing a phenomenon known as 'Marble Cancer'.

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Alternative Fuels: The use of diesel and petrol as fuels in automobiles is being replaced by CNGCNG (Compressed Natural Gas), because CNGCNG produces harmful products in very small amounts and is a cleaner fuel.

📐Formulae

C+O2→CO2+HeatC + O_2 \rightarrow CO_2 + \text{Heat}

2C+O2 (insufficient)→2CO+Heat2C + O_2 \text{ (insufficient)} \rightarrow 2CO + \text{Heat}

S+O2→SO2S + O_2 \rightarrow SO_2

SO2+H2O→H2SO3 (Sulphurous acid)SO_2 + H_2O \rightarrow H_2SO_3 \text{ (Sulphurous acid)}

CaCO3+H2SO4→CaSO4+H2O+CO2CaCO_3 + H_2SO_4 \rightarrow CaSO_4 + H_2O + CO_2

💡Examples

Problem 1:

Why is it advised never to sleep in a closed room with a coal fire burning inside?

Solution:

In a closed room, the supply of oxygen (O2O_2) is limited. This leads to the incomplete combustion of coal, producing Carbon Monoxide (COCO) gas.

Explanation:

Carbon Monoxide (COCO) is a toxic gas that binds with hemoglobin in the blood more strongly than oxygen, forming carboxyhemoglobin. This prevents the transport of oxygen to body parts, leading to suffocation and potentially death.

Problem 2:

Explain how the burning of fossil fuels contributes to the damage of the Taj Mahal.

Solution:

The burning of coal and petroleum releases SO2SO_2 and NO2NO_2. These gases react with water vapor in the atmosphere to form H2SO4H_2SO_4 and HNO3HNO_3, resulting in acid rain.

Explanation:

Acid rain reacts with the marble (CaCO3CaCO_3) of the Taj Mahal. The reaction is: CaCO3+H2SO4→CaSO4+H2O+CO2CaCO_3 + H_2SO_4 \rightarrow CaSO_4 + H_2O + CO_2. This corrodes the marble, turning it yellow and creating pits, a process called 'Marble Cancer'.