What color change indicates the presence of CO2 when using Bromothymol blue?

What color change indicates the presence of CO2 when using Bromothymol blue?

• A. Blue
• B. Green
• C. Yellow
• D. Red

Answer: (C)

Bromothymol blue is a pH indicator that changes color depending on the acidity of the solution. In the context of measuring carbon dioxide (CO2) concentration, the presence of CO2 results in the formation of carbonic acid when it dissolves in water, which increases the acidity of the solution. When the pH of the solution decreases due to this acidity, Bromothymol blue transitions from blue to yellow as it responds to the lower pH. A yellow color indicates that the solution is acidic, which confirms that CO2 is present. Conversely, if the solution is basic (higher pH), Bromothymol blue would appear blue. Therefore, the yellow color is the correct indicator that confirms the presence of CO2 in the solution due to its acidic effect.

Bromothymol blue is a pH indicator that changes color depending on the acidity of the solution. In the context of measuring carbon dioxide (CO2) concentration, the presence of CO2 results in the formation of carbonic acid when it dissolves in water, which increases the acidity of the solution.

When the pH of the solution decreases due to this acidity, Bromothymol blue transitions from blue to yellow as it responds to the lower pH. A yellow color indicates that the solution is acidic, which confirms that CO2 is present. Conversely, if the solution is basic (higher pH), Bromothymol blue would appear blue.

Therefore, the yellow color is the correct indicator that confirms the presence of CO2 in the solution due to its acidic effect.