4.14 - Chemistry (OpenStax)

Question

A 20.00ml sample of aqueous oxalic acid H₂C₂O₄ was titrated with a 0.09113M solution of potassium permanganate KMnO₄,

\(2MnO_4^ - \left( {aq} \right) + 5{H_2}{C_2}{O_4}\left( {aq} \right) + 6{H^ + } \to 10C{O_2}\left( g \right) + 2M{n^{2 + }}\left( {aq} \right) + 8{H_2}O\left( l \right)\)

A volume of 23.24 ml was required to reach the endpoint. What is the oxalic acid molarity?

Step-by-Step Solution

Answer

The molarity of oxalic acid is 0.2648M

Given data

From the given equation we can get the mole ratio of H₂C₂O₄:KMnO₄=C₂O₄:MnO₄-= 5:2 

Calculating millimoles

Millimoles of KMnO₄=0.09113mmol/ml x 23.24 ml= 2.1179 mmol

Millimoles of Oxalic acid = 2.1179 mol x 5/2 = 5.29475 mmol = 5.295 mmol (rounding off)

Molarity of oxalic acid = 5.295/20ml=0.26475M= 0.2648M (rounding off)