Question

5H₂O₂(aq) + 2MnO₄⁻(aq) + 6H⁺(aq) → 2Mn₂⁺(aq) + 8H₂O(l) + 5O₂(g)

In a titration experiment, H₂O₂(aq) reacts with aqueous MnO₄⁻(aq) as represented by the equation above. The dark purple KMnO₄ solution is added from a buret to a colorless, acidified solution of H₂O₂(aq) in an Erlenmeyer flask. (Note: At the end point of the titration, the solution is a pale pink color.)

Which of the following best describes what happens to the pH of the H₂O₂ solution as the titration proceeds?
A- The +2 charge on the manganese ions maintains the acidity of the solution.
B- The production of water dilutes the solution, making it basic.
C- As H⁺ ions are consumed, the solution becomes less acidic and the pH increases.
D- As H⁺ ions are consumed, the solution becomes less acidic and the pH decreases.

Answer 1

As H⁺ ions are consumed during the titration of H₂O₂ with MnO₄⁻, the solution becomes less acidic, which results in an increase in pH. Option C is correct answer.

Step-by-step explanation:

The student asked what happens to the pH of the H₂O₂ solution as the titration with MnO₄⁻ proceeds. In the given reaction, hydrogen peroxide (H₂O₂) reacts with permanganate (MnO₄⁻) in the presence of acid (H⁺ ions) to produce manganese(II) ions (Mn²⁺), water (H₂O), and oxygen gas (O₂).

The pH change during this titration can be understood by looking at what happens to the H⁺ ions in the reaction. As the titration progresses, H⁺ ions are consumed to form water. This decreases the concentration of H⁺ ions in the solution, which means the solution becomes less acidic, and hence, the pH increases. Therefore, the correct answer is that as H⁺ ions are consumed, the solution becomes less acidic and the pH increases (Option C).

It's important to note that, as the pH increases, there is no indication that the solution becomes basic. The reaction produces water, which does not have a significant effect on making the solution basic. Also, the +2 charge on the manganese ions does not maintain the acidity of the solution as it's a product and does not affect the current pH directly. The produced water also does not dilute the solution to make it basic.