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?Express your answer with the appropriate units.

Answer 1

We must first write the half reactions change in oxidation state:

`\begin{gathered} Reduction:Mn^(7+)+3e\rightarrow Mn^(4+) \\ Oxidation:O^(-1)-1e\rightarrow O_2 \end{gathered}`

Concntration of KMnO4:

`\begin{gathered} c=\frac{molority\text{ }KMnO_4}{electrons\text{ }gained} \\ \\ c=(1.68M)/(3) \\ \\ c=0.56M \end{gathered}`

Calculating the mass of hydrogen peroxide:

`\begin{gathered} m(H_2O_2)=\frac{volume\text{ }(KMnO4)* conc.(KMnO4)* molar\text{ }mass\text{ }H2O2}{1000mL} \\ \\ m(H_2O_2)=(12.8mL*0.56M*34gmol^(-1))/(1000mL) \\ \\ m(H_2O_2)=0.24g \end{gathered}`

Mass is 0.24g