Question

2) The active agent in many hair bleaches is hydrogen peroxide. The amount of H2O2 in 13.2−g of hair bleach was determined by titration with a standard potassium permanganate solution:

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

(a) For the titration, how many moles of MnO4− were required if 32.3 mL of 0.195 M KMnO4 was needed to reach the end point? Write your answer to the correct number of significant figures. Enter your answer in scientific notation.

____*10^___mol MnO₄⁻

(b) How many moles of H2O2 were present in the 13.2 g sample of bleach? Write your answer to the correct number of significant figures.

______mol H2O2

Thank you!!!

Answer 1

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

number of moles of KMnO4 = concentration * volume of the solution

number of moles of KMnO4 = 0.195 mol/L * 32.3 * 10^-3 L

Moles of KMnO4 = 0.0062985

moles of KMnO4 = 6.2985 * 10^-3 moles.

molar mass of H2O2 = 34.0147 g/mol

number of moles of H2O2 = 13.2g / 34.0147g/mol

number of moles of H2O2 = 0.38806mol

number of moles of H2O2 = 0.388 mol (since the original mass has only three significant figures)