CHEM1100 Experiment 5 Laboratory ReportCLEAN CHEMISTRY- Determination of sodium percarbonate concentration by

permanganate analysis

Name Emma Whittle Student Number 43584794Partner Emily Lay Demonstrator Chris ReadGroup P01 Date lab completed 13/10/14

Introduction: State the purpose of the experiment and background.

Hydrogen peroxide (H2O2), a key ingredient in laundry detergents, removes stains by acting as an oxidiser and breaking up molecules. When sodium percarbonate is added to water, hydrogen peroxide is released. In this experiment, we will be investigating the pairing of sodium percarbonate with potassium permanganate solution to effectively remove stains. The purpose of the experiment was to explore the reaction between hydrogen peroxide and permanganate. The reaction unbalanced that yields this reaction is;H+(aq) + H2O2(aq) + MnO4- (aq) O2 (g)+ H2O(l) + Mn2+(aq)Using a UV- vis spectroscopy, which indicates the presence of a particular species in a solution through absorbance, the molar ratio for the reaction and the concentration of H2O2 present in a sample of laundry powder will be determined.

Experimental Section: Include a short general description of the experiment. Remember to use the past tense.

Safety precautions taken; Gloves, closed in shoes, lab coat, safety glasses.Part A and B were completed and the results were recorded, needed for part C.Firstly to neutralise the base, the solutions were prepared.Around 0.3-0.4g of bleach powder was first measured and 1M sulfuric acid solution was added until the fizzing had come to a stop. This solution was then added to a 100mL volumetric flask and diluted with distilled water.To create a second dilution, 1mL of the solution was added using an automatic pipette into a 25mL volumetric flask and filling with distilled water. Three 10mL plastic tubes were prepared with 2.5mL of 1M H2SO4 (aq) and 2.5mL of of 4x10-4 M MKnO4 (aq).Bleach powder solution of 1mL was added to each of the tubes with an automatic pipette and filled to the 10mL mark with distilled water. The absorbance value on the calorimeter was re-zeroed to distilled water which had been done in part B.The absorbance values were then measured for all three tubes, as done before on the calorimeter connected to LabQuest.The average was taken from the three absorbance values and calculations were completed to calculate the stoichiometry of the solution;

1. The number of moles of Hydrogen Peroxide in solution that reacted.2. The Concentration of Hydrogen Peroxide in the two solutions.3. The number of moles of Hydrogen Peroxide in the active oxygen laundry powder.4. Percentage by mass of Na2CO3.1.5H2O2 in the laundry powder.

A report was written up.

Results Section: Show the steps in your calculations in each part. Use the flowchart on page 4 as a guide. Remember to include appropriate working and units.

a.Average absorbance from the triplicate analysis

Average= 0.069+0.072+0.063

3∴ =0.068

b.

Number of moles of H2O2 in solution (use equation from line of best fit)

Best fit Equation ;y= -2409.1x + 0.1032When y=0.0680.068= -2409.1x +0.1032 ∴ x= 1.461x10-5 M

c.[H2O2] in the diluted bleach solution

C=n/V 1mL= 0.001LC=1.461x10-5 / 0.001=0.0146 mol/L

d.[H2O2] in the 100 mL bleach soltion before dilution

C1V1=C2V2(0.0146 )(0.025) = C2(0.001)C2= 0.365 mol/L

e.Number of moles of H2O2 in the 100 mL bleach solution

n=CVn= 0.365 x 0.1=0.0365 M

f.Number of moles of H2O2 in bleach powder added

Same as the 100mL bleach solution;=0.0365 M

g. Molar mass of H2O2

MW= (2xH) + (2xO)= (2x1.008) + (2x 15.999)= 34.0147g/mol

h.Weight of H2O2 in bleach powder added

M= n x MMM= 0.0365 x 34.0147=1.24g

i.Percentage of H2O2 in bleach powder

Percentage= (1.24/0.319) x100= 388.71%

j.Molar mass of Na2CO3·1.5H2O2

MW= (2xNa)+(C)+(Ox3)+1.5((2xH)+(2xO))MW= (22.989x2)+(12.01)+(15.999x3)+(34x1.5)=157 g

k.% by mass of Na2CO3·1.5H2O2 in bleach powder

n= (3.65 x 10-3 M)/(1.5)= 2.43x10-3

m= 2.43x10-3 x 157= 0.38Percentage = (0.38/0.319)x100=119.12 %

Discussion Section: You must state the overall (main) outcome of the experiment. Include an evaluation of any sources of error and take into account how these might have affected your final results.

The outcome of the experiment was to determine the concentration and stoichiometry of sodium percarbonate by permanganate analysis. It has been calculated that the hydrogen peroxide present in the bleach power was 388.71% and also the percent yield by mass of Na2CO3.1.5H2O2 in the unknown bleach powder was 119.12%.

These percentage mass could not correct as it is over 100%, this means there is high inaccuracy in our results. When this was compared to other groups, the inaccuracy was more evident since the result should be a much lower percentage around 30-40%.

This is the product of the reaction of hydrogen peroxide and permaganate;

6H+(aq) + 5H2O2(aq) + 2MnO4-(aq) → 5O2(g) + 6H2O(l) + 2Mn2+(aq)

There were many sources of error that could have affected the final result. An impacting inaccuracy was the preciseness of measurements to create each solution. To improve this error, an automatic pipette and volumetric pump was used. However, errors were introduced during the dilution and transfer of bleach powder into the solutions. This error affected the accuracy of our stoichiometry and as a result our calculations and percentage mass for the experiment. This would further affect the spectrometer and wavelength if the measurements were incorrect.

Another reason the percentage was very high could be due to the low absorbance average from the triplicate analysis. The UV-vis spectrometer may of needed a more often calibration with the distilled water to get a more accurate absorption value.

Multiple trials may also improve accuracy and reduce the effects of random error.

Despite this error, an accurate trendline and concentration gradient was able to be developed for absorption and the molar ratio between hydrogen peroxide and permanganate was able to be calculated.

References: Go to the UQ Library website. In the Search box, type “Percarbonate as a hydrogen peroxide carrier”. Follow the Harvard referencing style to provide a full reference for the article for which Javier Rivas is a co-author.

Calle, RG, Gimeno, O, Rivas, J, 2012, ‘Percarbonate as a Hydrogen Peroxide Carrier in Soil Remediation Processes’, Environmental engineering science, vol. 29, pp. 951-956.