Question

Reason for rising of the water in bent test tube in the set-up of experiment to show that CO₂, is produced during respiration by use of KOH is

• A. Water always rises up
• B. A vacuum is created in conical flask due to absorption of CO₂, by KOH solution to fill it up as the water rises up in bent tube
• C. Water does not rise up in the bent tube
• D. Due to KOH solution.

Answer 1

The correct option is B

A vacuum is created in conical flask due to absorption of CO₂, by KOH solution to fill it up as the water rises up in bent tube

The correct option is (B).

Explanation for the correct answer

1. Respiration is the process of consuming carbohydrates to release carbon dioxide (CO₂) and energy.
2. KOH (potassium hydroxide) absorbs CO_2, which creates a vacuum in the flask.
3. The vacuum draws up the water level in the bent tube.

The explanation for incorrect answers

Option (A)

1. KOH absorbs carbon dioxide released by the germinating seeds; this creates a vacuum that creates a pressure difference for the water molecules to move up into the tube.
2. Water does not have the property to move upwards in normal conditions.

Option (C)

1. There would be no vacuum if the KOH were not present in the conical flask to absorb carbon dioxide.
2. In that condition, the water remains in the beaker and does not move up into the tube.
3. Unfortunately, this is not the case. Thus, the water rises into the bent tube.

Option (D)

1. Water does not rise due to KOH, but the reason for its rise is the vacuum created by the action of KOH.

The vacuum creates a pressure difference for the water molecules to move up.