Draw Diagram.

Question 15 Marks

With the help of ne abelled diagram explain the following : Biogas plant.

Answer

Animal dung, dry leaves, wet garbage get decomposed by anaerobic microbes in a biogas plant.
This produces methane gas, also called biogas.
Biogas is a very cheap fuel option which meets the demand for cooking gas. It is also used for the production of electricity.
Biogas contains about 55% to 60% methane and the rest is carbon dioxide.
Biogas is a fuel which is convenient to use and, in addition to this, a very good manure is also produced as a side product of the process.
Biogas production process – Production of biogas is an anaerobic process. It takes place in two stages.
(a) Production of acids – The microbes act on the biodegradable complex organic compound and produce organic acids.
(b) Methane gas production – The methanogenic bacteria act on the organic acids to produce methane gas.

Question 25 Marks

With the help of ne abelled diagram explain the following : Regular fire extinguisher.

Answer

A fire extinguisher contains Sodium bicarbonate powder. There is also dilute sulphuric acid placed in a glass capsule.
On pressing the knob, the capsule breaks and sulphuric acid comes in contact with the sodium bicarbonate. These two react chemically to release $CO_2$ which comes out.
$CO_2$ based fire extinguishers do not cause corrosion and are non-conductors of electricity. Therefore, they are used when electrical or electronic equipment catches fire.
$CO_2$ based fire extinguishers are used to extinguish small scale fire. It is beyond their capacity to extinguish a big fire.
In modern fire extinguishers liquid and solid $CO_2$ is filled under pressure. On reducing the pressure, it becomes gaseous and comes out forcefully through the horn-like hose pipe.
Chemical reaction:

Science Draw Diagram.