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 21.8 mL of the KMnO4 solution?

Answer 1

Balanced chemical equation is:

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

lets calculate the mol of KMnO4

volume , V = 21.8 mL

= 2.18*10^-2 L

use:

number of mol,

n = Molarity * Volume

= 1.68*2.18*10^-2

= 3.662*10^-2 mol

According to balanced equation

mol of H2O2 reacted = (1/2)* moles of KMnO4

= (1/2)*3.662*10^-2

= 1.831*10^-2 mol

This is number of moles of H2O2

Molar mass of H2O2,

MM = 2*MM(H) + 2*MM(O)

= 2*1.008 + 2*16.0

= 34.016 g/mol

use:

mass of H2O2,

m = number of mol * molar mass

= 1.831*10^-2 mol * 34.02 g/mol

= 0.6229 g

Answer: 0.623 g