Redox titrations are used to determine the amounts of oxidizing and reducing age

Question

Redox titrations are used to determine the amounts of oxidizing and reducing agents in solution. For example, a solution of hydrogen peroxide, H_2O_2, can be titrated against a solution of potassium permanganate, KMnO_4. The following equation represents the reaction: 2KMnO_4 (aq) + H_2 O_2(aq) + 3H_2SO_4(aq) rightarrow 3O_2(g) + 2MnSO_4(aq) + K_2SO_4(aq) + 4H_2O(1) A certain amount of hydrogen peroxide was dissolved in 100. mL of water and then titrated with 1.68 M KMnO_4. What mass of H_2 O_2 was dissolved if the titration required 22.3 mL of the KMnO_4 solution?

Explanation / Answer

Stoichiometry ratio of H2O2 and KMnO4 is 1:2

Molarity = moles / volume (in Liters) then

moles KMnO4 = (molarity of KMnO4)(volume of KMnO4 in Liter)

moles KMnO4 = (1.68 M) (0.0223 L)

moles of KMnO4 = 0.037464

For every 1 mole of H2O2, 2 moles of KMnO4 are needed

Therefore:

moles H2O2 = 0.037464 / 2

moles H2O2 = 0.018732

Mass = moles x (molar mass)

Mass of H2O2 = 0.018732 x 34.016

mass H2O2 = 0.637 grams

Therefore 0.637 grams of H2O2 was dissolved in 100.0 mL of water.

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