Identify the components and process.

The setup demonstrates anaerobic respiration (fermentation) by yeast in a sugar solution. Yeast breaks down sugar to produce ethanol and carbon dioxide. The carbon dioxide gas is then passed into lime water.

Lime water (calcium hydroxide solution) is used to detect carbon dioxide. When carbon dioxide is bubbled through it, the lime water turns cloudy or milky.

The observations made in the lime water are:

• The lime water turns cloudy or milky.
• Bubbles are observed in the lime water.

Yeast (Substance D) in the sugar solution undergoes anaerobic respiration (fermentation) at 40°C. This process produces carbon dioxide gas.

The carbon dioxide gas produced by the yeast is bubbled through the delivery tube into the lime water. Carbon dioxide reacts with the calcium hydroxide in the lime water to form insoluble calcium carbonate, which appears as a white precipitate, causing the cloudiness.

The explanation for the observations is:

• Yeast carries out anaerobic respiration (fermentation) in the sugar solution, producing carbon dioxide gas.
• The carbon dioxide gas bubbles through the delivery tube into the lime water.
• Carbon dioxide reacts with calcium hydroxide (lime water) to form insoluble calcium carbonate, which precipitates out and causes the lime water to turn cloudy. The chemical reaction is: