• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Analysis of Two Brands of Commercial Bleaches

Extracts from this document...

Introduction

PLK TANG YUK TIEN COLLEGE ADVANVED LEVEL CHEMISTRY (TAS) EXPERIMENT 3 Analysis of Two Brands of Commercial Bleaches Objective To determine the concentration of sodium chlorate(I) (NaClO) in two commercial bleaches and compare the two bleaches on both concentration and price. Procedures 1. 10.0 cm3 of the bleach "KAO" was pipetted into a clean 250 cm3 volumetric flask. It was made up to the mark using deionized water. 2. 25.0 cm3 of the diluted solution was pipetted into a conical flask. 3. 10 cm3 of 1 M potassium iodide solution and 10 cm3 of dilute sulphuric acid was added into the conical flask also. 4. The mixture in the conical flask was titrated against the 0.0992 M sodium thiosulphate solution. 5. Three drops of freshly prepared starch indicator are added into the conical flask when the reaction mixture turned pale yellow . 6. The mixture was titrated to the end-point. 7. At the end point, the solution turned from dark blue to colourless. 8. Steps (1) to (7) were repeated with another bleach "LION" Results Concentration of standard sodium thiosulphate solution : 0.0992M Brand 1 Trade Name : KAO Bleach Price : $7.33per dm3 ($11/1500mL) ...read more.

Middle

of mole of S2O32- )/2 =0.00069936mol ?no. of mole of OCl- in10 cm3 solution = no. of mole of I2 x10 =0.00069936x10 =0.0069936mol ?Mass of OCl- contained in 10 cm3 solution=0.0069936x(16+35.45) =0.35982072g ?Concentration of OCl- (active ingredient available) =0.35982072/(10/1000)=35.98gdm-3 1b)For KAO Bleach, Cost per one gram of OCl- = 11 /[29.474676x(1500/1000)] =$0.277/g For LION Bleach, Cost per one gram of OCl- = 10 /[35.982072x(1500/1000)] =$0.185/g 2. Based on the calculated results, decide which of the two brands of bleach is a better buy. When compring the costs per one gram of OCl- of KAO(0.277/g) and LION($0.185/g), as we can pay a lower price ($0.185)to buy the same weight of active ingredient (OCl- ) in LION bleach, LION bleach is a better buy. 3. Explain why potassium iodide and sulphuric acid must be in excess. ClO-(aq) + 2I-(aq) + 2H+(aq) � I2(aq) + H2O(l) + Cl-(aq) From the equation above, iodide ions and hydrogen ions react with Hypochlorite ions to form iodine ,water and chloride ions.To determine the actual number of mole of ClO- ,all ClO- ions sholud react to give iodine. ...read more.

Conclusion

When sodium hypochlorite is heated or evaporated, sodium chlorate and sodium chloride will be formed. Chemical equation: 3 NaOCl(aq) � NaClO3 (aq)+ 2 NaCl(aq) 5. The starch indicator should not be added too early. Why? Starch is often used in chemistry as an indicator for redox titrations where iodine is present as starch forms a very dark blue-black complex with iodine. Moreover,the indicator is not affected by the presence of iodide (I-). In order for the the starch solution to change colour, both starch and iodide must be present. Starch forms an unstable complex which is blue coloured in low concentrations of iodine. However, this complex is in high concentrations of iodine . If starch solution is added too early, the conical flask still contains high concentration of iodine.As a result, highly stable complex is formed,the starch indicator then cannot be decolourised and the complex will spoil the reaction medium. Consequently, the titration cannot continue. Therefore the iodine must be diluted first with the titrant ,sodium thiosulphate to ensure no higly stable complex is formed.After that the starch can be added. The End ?? ?? ?? ?? F.6 Chemistry TAS/Experiment 3/P.1(3) 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Physical Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a star student thought of this essay

5 star(s)

Response to the question

The response to the question is done to a very high level. With the combination of accuracy and scientific detail the experiment is flawless in calculations. The improvements would be to add an evaluation of where the experiment could have ...

Read full review

Response to the question

The response to the question is done to a very high level. With the combination of accuracy and scientific detail the experiment is flawless in calculations. The improvements would be to add an evaluation of where the experiment could have been improved and what errors may have occurred to show an understanding of how the experiment went.

Level of analysis

The candidate should include in their introduction why they are examining sodium chlorate(I) in their experiment, such as what significance this has to the action of the bleach. The procedure is recorded very clearly and would be easy to follow. The questions are answered to a very high level of detail and the calculations are all correct. Decimal places lack consistency in places.

Quality of writing

Grammar, spelling and punctuation to an high standard. Good, clear format.


Did you find this review helpful? Join our team of reviewers and help other students learn

Reviewed by skatealexia 29/07/2012

Read less
Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Physical Chemistry essays

  1. Marked by a teacher

    Heat of Neutralization. Objective: To investigate the ...

    5 star(s)

    This was because we assumed heat was instantly exchanged at the time of mixing. Thus, the ?T we used in the calculations are the ?T at mixing time. Notice that no reasonable temperature readings could be taken at the time of mixing, therefore we needed to assume that the temperature

  2. Determination of isoelectric point of protein (casein).

    The shape of the cluster is related to the fundamental geometric arrangement of the functional group that determines the precise molecular structure of casein. If the isoelectric point of casein is approximately pH 4.7, it suggests that the side

  1. Law of conservation of matter lab report.The chemical reaction used to research is: ...

    the product formed does not change, but in this case there are little differences in the mass of the product formed and the calculated mass of the product. The gradient of line of best fit is 1.0024, which is approximately 1.

  2. Investigation to analyse some fruit and vegetable juices for the contents present in them.

    constituting the protein. 4. UNSATURATION The unsaturation in the organic compounds is due to the presence of double or triple bonds in its constituent compounds. Identification test Sulphuric acid Test In this test, the compound is taken in a clear test tube and conc.

  1. Acid-base titration. Objective To determine the concentration of sulphuric acid (H2SO4) using sodium ...

    Choice of indicator Methyl orange instead of phenolphthalein was used in the titration since H2SO4 is a strong acid whereas Na2CO3 is a weak alkali. An ideal indicator for a titration is one whose end point matches the equivalence point, which is the point at which equivalent amounts of the acid and alkali have reacted.

  2. An Introduction to Qualitative Analysis

    Na3PO4 would not be useful to identify cation because the anion of PO43- is not soluble and form precipitate with any cations. Data and Observations: Part I -Qualitative Analysis of Group 2 Elements Table 1 REAGENTS 0.1M SOLUTIONS OF GROUP 2 CATIONS (AS NITRATES)

  1. Determination of the Percentage of Oxalate in Iron(II) Oxalate by Redox Titration

    But doing so needs a lot of time. How can we shorten the time required for heating the solution up to 60oC? There are 2 ways. First, we can heat the conical flask with a stronger flame. We can adjust the flame intensity by enlarging the air hole.

  2. How are standard solutions prepared & how is titration carried out in industry

    to the end point and absorbance/titrant volume beyond the end point, will intersect at the equivalence point. The accuracy of this method is brought into questions, when the absorbance level is high. The percentage transmittance (%T) of the selected wavelength is low, and so it is desirable to choose lower

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work