Question

A student is doing a titration using potassium permanganate solution, KMnO4, to determine the amount of H2O2 in a sample. The balanced equation for the reaction in the titration is given below:2 MnO4-(aq) + 6 H+(aq) + 5 H2O2(aq) -->ž 2 Mn2+(aq) + 8 H2O(l) + 5 O2(g)A student calculates an amount of moles of H2O2 that is larger than the actual value. Which of the following errors could correctly explain the larger value?The student failed to wear goggles.The student did not swirl the flask appropriately and therefore stopped short of the endpoint.The student failed to rinse the buret with KMnO4¬ solution after rinsing it with distilled water.The student added an extra 15 mL of distilled water to the H2O2 solution.

Answer 1

Answer:

The student failed to rinse the buret with KMnO₄ solution after rinsing it with distilled water.

Explanation:

In a titration, the equivalent moles of titrant must be the same than analyte. If the student calculates an amount of moles of H₂O₂ that is larger than the actual value:

The student failed to wear goggles FALSE. The use of goggles doesn't change the results in the lab but you must use it!

The student did not swirl the flask appropriately and therefore stopped short of the endpoint. FALSE. The stopped short of the endpoint would explain a lower concentration of the real value.

The student failed to rinse the buret with KMnO₄ solution after rinsing it with distilled water. TRUE. If you don't rinse the buret with KMnO₄ solution the concentration of this solution in the buret will be lower than real concentration doing you spend more titrant volume overestimating the amount of H₂O₂ moles.

The student added an extra 15 mL of distilled water to the H₂O₂ solution. FALSE. The addition of water doesn't change the amount of H₂O₂ moles in the solution.

I hope it helps!