LabBench Activity

How the Respirometer Works

When the tip of the respirometer is submerged, no additional air will enter.

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As O2 is used up, the pressure of gases inside the respirometer decreases. This causes water to enter the pipette.

The CO2 that is produced combines with KOH to form a solid precipitate, K2CO3.

Notice that as the gas volume inside the vial decreases, the pressure of water outside the vial forces water into the pipette. Because the amount of water that enters the pipette is directly proportional to the amount of oxygen consumed by the cricket, measuring the water volume in the pipette allows you to measure the rate of respiration.