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:

$\begin{gathered} c=\frac{molority\text{ }KMnO_4}{electrons\text{ }gained} \\ \\ c=\frac{1.68M}{3} \\ \\ c=0.56M \end{gathered}$

Calculating the mass of hydrogen peroxide:

$\begin{gathered} m(H_2O_2)=\frac{volume\text{ }(KMnO4)\times conc.(KMnO4)\times molar\text{ }mass\text{ }H2O2}{1000mL} \\ \\ m(H_2O_2)=\frac{12.8mL\times0.56M\times34gmol^{-1}}{1000mL} \\ \\ m(H_2O_2)=0.24g \end{gathered}$

Mass is 0.24g