Redox titrations are used to determine the amounts of oxidiz

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 13.3 mL of the KMnO4 solution?

Solution

Balanced chemical equation is:
2KMnO4(aq)+H2O2(aq)+3H2SO4(aq)3O2(g)+2MnSO4(aq)+K2SO4(aq)+4H2O(l)


Here:
M(KMNO4)=1.68 M
V(KMNO4)=13.3 mL
V(H2O2)=100.0 mL

According to balanced reaction:
number of mol of KMNO4 =2*number of mol of H2O2
M(KMNO4)*V(KMNO4) =2*M(H2O2)*V(H2O2)
1.68*13.3 = 2*M(H2O2)*100.0
M(H2O2) = 0.1117 M

volume , V = 100 mL
= 0.1 L


use:
number of mol,
n = Molarity * Volume
= 0.1117*0.1
= 1.117*10^-2 mol

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
= 1.117*10^-2 mol * 34.016 g/mol
= 0.380 g
Answer: 0.380 g