In the experimental set up to show that CO2 is given out during respiration, name the substance taken in the small test tube kept in the conical flask. State its function and the consequence of its use.

The substance taken in the small test tube kept in the conical flask is potassium hydroxide (KOH) solution.

Function:
Potassium hydroxide solution absorbs carbon dioxide (CO2). It reacts with CO2 to form potassium carbonate (K2CO3) and water (H2O). The chemical equation for this reaction is:
2KOH(aq) + CO2(g) → K2CO3(aq) + H2O(l)

Consequence of its use:
The absorption of CO2 by the potassium hydroxide solution leads to a decrease in the pressure inside the conical flask. This pressure decrease is observed as a rise in the level of the liquid (usually water or coloured water) in the delivery tube connected to the conical flask. This rise in the liquid level demonstrates that CO2 has been produced during respiration. Without the KOH solution, the CO2 produced would remain in the flask and would not create the pressure difference needed for this demonstration.