Question

If a solution is undergoing a reaction where CO2 is being used as a reactant, what color is the phenol red-containing solution shifting toward?

a.)pink
b.)colorless
c.)red
d.)green
e.)yellow

Answer 1

Phenol red is a pH indicator that changes color in response to changes in acidity or basicity of a solution. In acidic solutions, phenol red is yellow, while in basic solutions, it is pink.

If a solution is undergoing a reaction where CO2 is being used as a reactant, it means that the CO2 is being consumed and converted into some other product(s). One of the products of this reaction is likely to be a base, since CO2 is an acidic gas and tends to form acidic solutions when it reacts with water. Therefore, the solution is likely to become more basic as the reaction proceeds.

As the solution becomes more basic, the phenol red indicator will shift from its original yellow color towards pink. Therefore, the answer is (a) pink.