DCP+CE Analysis of a Hydrogen Peroxide Solution

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Background

An acidified solution of manganate (VII) ions or permanganate is a strong oxidizing agent and is often used for analysis of solutions for ferric ions (Iron (III)), by reducing the ferric to ferrous, and then titrating with a permanganate solution of known concentration.  The relevant half equations are:

Potassium permanganate solutions have a short shelf life.  Their decomposition is catalysed by light, heat, acids, bases Mn (II) and MnO2. Thus, potassium permanganate solutions need to be standardized immediately prior to use to determine their precise concentration.  A primary standard is a substance that is available in pure form, is not hygroscopic and is easily dried, is stable in both pure form and in solution.  Sodium oxalate (Na2C2O4) is a white crystalline solid and is readily available in pure and stable form.  The titration is usually carried out at 70 ºC so that the rate of reaction is sufficiently fast.  The solution temperature should remain above 60 ºC at the end point.

Hydrogen peroxide is regarded as an "environmentally friendly" alternative to chlorine for water purification and wastewater treatment.  Because hydrogen peroxide decomposes in the presence of heat, light, or other catalysts, the quality of a hydrogen peroxide solution must be checked regularly to maintain its effectiveness.

        Table 1. Equipments and uncertainties

Results:

        Table 2. Raw Data – 1st Titration on NaC2O4+H2SO4 with KMnO4

        

        Table 3. Raw Data – 2nd Titration on H2O2 + H2SO4 with KMnO4

        Table 4. Processed Data – Amount of KMnO4 Added in Both of the Titration Trials

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Uncertainty for calculating the amount of KMnO4

        Adding absolute uncertainty

        44.5ml±0.0750ml – 23.0ml±0.075        = (45.4ml – 23ml) ± (0.0750ml +                                                                             0.0750ml)

                                                = 21.50ml ±0.15ml

        Table 5. Processed Data – Average of 1st Titration and 2nd Titration

Uncertainty for calculating the average amount of moles for NaC2O4 in 1st titration

        Dividing absolute uncertainty

(0.30g±0.02g) / (23+23+16+16+16+12+12) = (0.30g±0.067%)/ (23+23+16+16+16+12+12)

                                                    = 0.30/134 ± 0.067%+0%

                                                    = 0.0022 ± 0.0067%

                                                    = 0.0022mol ± 1.8x10-7mol

        Adding absolute and dividing absolute uncertainty

0.0022±1.8x10-7mol  + 0.0023±1.8x10-7mol  + 0.0023±1.8x10-7mol  + 0.0022±1.8x10-7mol  + 0.0025±1.8x10-7mol  + 0.0026±1.8x10-7mol        

= (0.0022 + 0.0023 + 0.0023 + 0.0022 + ...

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