Question

A potassium permanganate solution is prepared by dissolving 22.14g of KMnO4 in water and diluting to a total volume of 1.000 L. A total of 20.50 mL of this solution is required to reach the endpoint in a titration of a 200.0-mL sample containing H2C2O4(aq). Determine the concentration of H2C2O4 in the original solution. _________M

Answer 1

Answer:

The concentration of H₂C₂O₄ is 7,1800x10⁻³ M

Explanation:

The reaction of the titration is:

2 KMnO₄ + H₂C₂O₄ → 2 CO₂ + K₂O + 2 MnO₃ + H₂O

22.14g of KMnO₄ in 1,00L of water have a molarity of:

22,14g KMnO₄/L×$\frac{1mol}{158,034g}$ = 0,14 M of KMnO₄

The moles you required for a complete reaction are:

0,14 mol KMnO₄/L× 0,02050L = 2,872x10⁻³ mol KMnO₄

By the reaction 2 moles of KMnO₄ reacts with 1 mole of H₂C₂O₄, thus, the moles of H₂C₂O₄ that react were:

2,872x10⁻³ mol KMnO₄×$\frac{1mol H_{2}C_{2}O_{4}}{2molKMnO_{4}}$ = 1,436x10⁻³ moles of H₂C₂O₄

As the volume of the sample was 200,0mL≡ 0,2000L, The concentration of H₂C₂O₄ is:

$\frac{1,436x10^{-3} mol}{0,2000L}$ = 7,1800x10⁻³ M

I hope it helps!