Why heating is not required in f.a.s. and potassium permanganate titration

Redox Titrations • In a titration, the concentration of a solution is determined by titrating with a solution of known concentration. • In redox titrations, an oxidising agent is titrated against a reducing agent • Electrons are transferred from one species to the other • Indicators are sometimes used to show the endpoint of the titration • However, most transition metal ions naturally change colour when changing oxidation state • There are two common redox titrations you should know about manganate(VII) titrations and iodine-thiosulfate titrations Potassium manganate(VII) titrations • In these redox titrations the manganate(VII) is the oxidising agent and is reduced to Mn 2+(aq) • The iron is the reducing agent and is oxidised to Fe 2+(aq) and the reaction mixture must be acidified, to excess acid is added to the iron(II) ions before the reaction begins • The choice of acid is important, as it must not react with the manganate(VII) ions, so the acid normally used is dilute sulfuric acid • As it does not oxidise under these conditions and does not react with the manganate(VII) ions • You could be asked why other acids are not suitable for this redox titration in the exam so make sure you understand the suitability of dilute sulfuric acid Indicator and end point • Potassium permanganate acts as its own indicator, as the purple potassium permanganate solution is added to the titration flask from the burette and reacts rapidly with the Fe 2+(aq) • The burette used in this pra...

Table of Contents • • • • • • • • • • Why is it not necessary to maintain the temperature at 60 C throughout the titration? Explanation: All reactions during the titration needs activation energy. The preheating up to 50-60°C during the titration will provide the enough kinetic energy. The heated mixture can have the higher frequency of collision among the particles. Why should you heat the oxalic acid solution to about 60 70 C before titration with KMnO4 solution? Oxalic acid is heated before titration with KMnO4 solution because this reaction happens only in certain temperature. If not heated your light pink titrated solution turns brown soon & reaction takes longer times but overheating will cause decomposition of oxalic acid as CO2. Why do we need to heat sodium oxalate solution at 80 90 degree Celsius in the standardization of KMnO4? 3) Solution of sodium oxalate is heated because the reaction on addition of potassium permanganate should be fast. What temperature is maintained during titration of oxalic acid and potassium permanganate in acid solution why it is maintained? 50-60’C. KMnO4 is a dark colour solution so always use upper meniscus reading. Use sulphuric acid for acidifying the potassium permanganate. Don’t use HCl or nitric acid. Maintain the temperature of oxalic acid solution at 50-60’C. Why do we heat oxalic acid solution while titration? We heat oxalic acid solution because without heating it is a slow process as an energy greater than the activation en...