The active agent in many hair bleaches is hydrogen peroxide. The amount of H_2O_

Question

The active agent in many hair bleaches is hydrogen peroxide. The amount of H_2O_2 in 14.7-g of hail bleach was determined by titration with a standard potassium permanganate solution: For the titration, how many moles of MnO4 were required if 43.6 mL of 0.186 M KMnO_4 was needed to reach the end point? Write your answer to the correct number of significant figures. Enter your answer in scientific notation. How many moles of H_2O_2 were present in the 14.7 g sample of bleach? Write your answer to the correct number of significant figures.

Explanation / Answer

a) millimoles of KMnO4 used for the titration = V x M

= 43.6mL x 0.186

= 8.1096mmoles

= 8.11x10-3  moles

b) equivlents of KMnO4 used in titration = equivlents of H2O2 present in sample.

OR

moles of KMno4 x 5 = 2 x moles of H2 O2

8.11x10-3 x 5/2 = moles of H2 O2

Thus moles of H2 O2 present in the sample = 20.275x10-3

= 2.03x10-2  moles

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