CHEMISTRY [3 Mark Question Answer]

Five measures for the prevention of air pollution are:

1. By using smokeless sources of energy, like solar energy and electrical energy, in place of conventional fossil fuels.
2. By using filters for the. smoke coming out of the chimneys of factories and power plants.
3. By using internal combustion engines in vehicles for complete and efficient burning of fuel.
4. By locating industries away from residential areas.
5. By growing more trees.

Take manganese dioxide in a round bottom flask and add hydrogen peroxide drop by drop to it, which acts ; a catalyst as shown in the figure. Collect oxygen by downward displacement of water.

Difference between rusting and burning

Rusting	Burning
Rusting is the process in which iron slowly reacts with oxygen in the air and produces a flaky substance called rust. Air and moisture are necessary for rusting.	Burning is fast oxidation process in which large amount of energy is produced. Only air is necessary for burning.

Two useful applications of greenhouse effect are:
1. Growing vegetables and flowers in snow-bound regions:
Sheds using glass walls are built which allow smaller wavelength of solar heat radiations to pass into the shed but does not allow the longer wavelength of heat radiations to pass out during night. This keeps the shed reasonably warm for flowers and vegetables to grow.
2. Use of glass in keeping homes warm:
In cold countries, the glass windows and doors allow the smaller wavelength of heat radiations of solar energy to pass into the rooms but does not allow longer wavelength of heat radiations to pass out. Thus, greenhouse effect takes place and rooms keep reasonably warm.

Uses of oxygen are :

• Spaceships: Liquid oxygen is used for burning fuel in rockets and spaceships as there is no air in the space.
• Cutting and welding :Oxygen and hydrogen are made to bum in a specially designed torch. The oxy- hydrogen flame can easily melt metals and used for cutting and welding them.
• Chemical industry :Oxygen is used in large amount for preparing sulphuric acid from sulphur and nitric acid from ammonia.