2) The active agent in many hair bleaches is hydrogen peroxide. The amount of H2

Question

2) The active agent in many hair bleaches is hydrogen peroxide. The amount of H2O2 in 13.2g 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!!!

Explanation / Answer

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)

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