Mercury (Hg) is generally used in anaerobic respiration experiments because it does not react with CO2.

Explanation:
Anaerobic respiration is a type of cellular respiration that occurs in the absence of oxygen. It is the process by which cells produce energy in the form of ATP without the use of oxygen. During anaerobic respiration, glucose is broken down into pyruvate through a series of chemical reactions.

One of the byproducts of anaerobic respiration is carbon dioxide (CO2). CO2 is produced when pyruvate is converted into various end products, such as lactic acid in humans or ethanol in yeast. It is important to measure the production of CO2 in anaerobic respiration experiments to determine the efficiency of the process and to understand the metabolic pathways involved.

Mercury (Hg) is a chemical element that is known for its low reactivity. It is a heavy metal that is liquid at room temperature and has a high density. Due to its low reactivity, mercury does not readily react with CO2 or other gases in the air. This makes it an ideal substance to use in anaerobic respiration experiments because it does not interfere with the measurement of CO2 production.

By using mercury as a trapping agent in anaerobic respiration experiments, the CO2 produced by the cells can be collected and measured accurately. This allows researchers to study the rate of CO2 production and determine the efficiency of anaerobic respiration under different conditions.

In conclusion, mercury is used in anaerobic respiration experiments because it does not react with CO2. This property allows for accurate measurement of CO2 production, which is crucial for understanding the metabolic pathways involved in anaerobic respiration.