Question

An experimental set up is given to demonstrate that CO₂ is given out during respiration. Four students I, II, III and IV made the following observations:

1. Level of water remained the same in both the beaker and delivery tube.
2. Level of water increased in the delivery tube.
3. Level of water gets reduced in both the beaker and the delivery tube.
4. Water ascends in the delivery tube and again flows back into the beaker.

The correct observation is done by student

• A. I
• B. II
• C. III
• D. IV

Answer 1

The correct option is B

II

The correct option is B.

Explanation of correct option:

• In the experiment, germinated seeds release carbon dioxide during respiration.
• The KOH solution in the tube absorbs the carbon dioxide, which creates a vacuum in the conical flask.
• The vacuum created in a conical flask pushes the water upwards in the delivery tube.

Explanation of incorrect options:

Option A:

• The vacuum created in the flask pushes the water upward, so the water level cannot remain the same.

Option C:

• Water is pushed upward when a vacuum is created, not downwards. Hence, this option is incorrect.

Option D:

• Respiration is a continuous process accompanied by a constant release of carbon dioxide. Hence, water cannot flow back downwards.

Therefore, the correct observation was done by the second student, who observed an increase in the water level in the delivery tube.