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, H2O2, can be titrated against a solution of potassium permanganate, KMnO4. The following equation represents the reaction: 2KMnO4(aq)+H2O2(aq)+3H2SO4(aq)3O2(g)+2MnSO4(aq)+K2SO4(aq)+4H2O(l) A certain amount of hydrogen peroxide was dissolved in 100. mL of water and then titrated with 1.68 M KMnO4. What mass of H2O2 was dissolved if the titration required 12.8 mL of the KMnO4 solution?

Explanation / Answer

2KMnO4(aq)+H2O2(aq)+3H2SO4(aq)3O2(g)+2MnSO4(aq)+K2SO4(aq)+4H2O(l)

2 moles          1 mole

KMnO4                                        H2O2

M1 = 1.68M                               M2 =

V1   = 12.8ml                               V2 = 100ml

n1 = 2                                         n2 =1

M1V1/n1     =   M2V2/n2

M2               = M1V1n2/n1V2

                     = 1.68*12.8*1/2*100 = 0.10752M

molarity of H2O2 = 0.10752M

no of moles of H2O2 = molarity* volume in L

                                   = 0.10752*0.1 = 0.010752 moles

mass of H2O2 = no of moles * gram molar mass

                       = 0.010752*34 = 0.3655g

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