Give an experiment to prove that carbon dioxide is released during respiration.

Give an experiment to prove that carbon dioxide is released during respiration.

Answer:

Respiration is a biochemical process in which the food is oxidised in order to release energy.

To prove that CO 2 is released during respiration, 

• We take germinating seeds which are actively respiring to produce CO 2 a
• And we use Potassium Hydroxide (KOH) to absorb this released CO 2 .
  The overall reaction is as follows:  

Materials Required:

Conical flask, U-shaped delivery tube (tube bent twice at right angles), cotton wool or moist blotting paper, water, thread, beaker, test tube, rubber cork with one hole, 20% freshly prepared KOH solution, vaseline, soaked gram seeds.

Procedure:

1. Take about 25-30 seeds of gram and germinate these seeds by placing them on moist cotton wool or moist blotting paper for 3-4 days.
2. Place the germinated seeds into a conical flask and sprinkle a little water in the flask to moist the seeds.
3. Take freshly prepared 20% KOH solution in a test tube and hang it in a conical flask with help of thread.
4. Close the mouth of the conical flask by placing a rubber cork containing one hole. .
5. Through the hole of rubber cork, insert one end of the U-shaped glass delivery tube in the conical flask and place the other end into a beaker filled with water.
6. Seal all the connections of the experimental set-up with vaseline so as to make it air-tight.
7. Mark the initial level of water in the U-shaped delivery tube.
8. Keep the apparatus undisturbed for 1-2 hours and note the change in level of water in the delivery tube.

Observation :

The level of water in the U-shaped delivery tube dipped in water of the beaker rises after sometime.   

Result:

• CO 2 is released by the germinating seeds during respiration in a conical flask. 
• This CO 2 is absorbed by KOH which is hanging inside the conical flask. 
• Due to absorption of CO 2 , a vacuum is created which causes an upward movement of water present inside the delivery tube which can be seen by change in level of water in that tube. 

Precautions:

1. Germinating seeds should be kept moist.
2. All connections of the set-up should be air-tight.
3. Freshly prepared KOH solution should be used.
4. Keep one end of the U-shaped delivery tube in a conical flask and the other end immersed in water of the beaker.
5. The test tube containing KOH should be hung carefully.