Question

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Answer 1

Answer:

List conditions under which combustion can take place.

Soln:

The burning of a substance in the presence of oxygen is defined as combustion.

The conditions under which combustion can take place are

• The presence of air or oxygen.
• The presence of fuel plays a significant role.
• Ignition temperature is maintained (It is defined as the substance that catches fire at its lowest temperature.)

(a) Burning of wood and coal causes Pollution of air.

(b) A liquid fuel, used in homes is Kerosene.

(c) Fuel must be heated to its Ignition Temperature before it starts burning.

(d) The fire produced by oil cannot be controlled by Water.

Explain how the use of CNG in automobiles has reduced pollution in our cities.

Soln:

CNG played an important role in reducing pollution among automobiles for the following reasons

CNG is comparatively a cleaner fuel.

The CNG can be an alternative for diesel, petrol and propane/LPG.

It usually contains a few undesirable gases than the other fuels mentioned above.

The combustion of fuels like petroleum causes many unburnt carbon particles along with carbon monoxide, which leads to respiratory diseases.

4. Compare LPG and wood as fuels

Soln:

Wood

It is considered as a traditional fuel used for both domestic and industrial purposes.

Wood produces a lot of smoke which pollutes the atmosphere and cause respiratory diseases.

The usage of wood to a large extent causes deforestation.

The calorific value of wood ranges between 17000 to 22000 kJ/kg

However, wood may be used as a furnace, stove or fireplace indoors while it is used for a campfire, furnace outdoors.

LPG

The usage LPG (Liquefied petroleum gas) has replaced wood.

It doesn’t release smoke and other pollutants.

It is a cleaner fuel.

The fuel efficiency of LPG is more than that of wood.

The calorific value of LPG is 55000 kJ/kg.

Hence, LPG is the most preferred choice.

Explanation:

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