Odoes the Reactio N Occur Again When More Hydrogen Perxide Is Added
Decomposing hydrogen peroxide
This Projection Folio start appeared in the September 1995 issue of Chemistry Review, Volume 5, Number 1, Page 30.
Note: Projection Page is designed to help y'all call back virtually your investigation. It is not intended to be a set of instructions for practical work and does not include a list of safety precautions. Chemistry REVIEW accepts no responsibility if Project Folio is used in any way as a fix of instructions.
The catalytic decomposition of hydrogen peroxide provides a range of project opportunities of varying length and complexity. This is because of the variety of catalysts that will increase the rate of decomposition and the methods that can exist used to monitor the reaction:
2H2O2 → 2HtwoO + Otwo
Using an enzyme catalyst
In many living organisms hydrogen peroxide is a production of metabolism that must be broken downwards, since in appreciable concentrations it is toxic. The rate of decomposition is increased by the intra-cellular enzyme catalase.
As a fairly simple project y'all could compare the effectiveness of the enzyme from dissimilar sources such as spud, celery and liver. This might lead yous on to a more than thorough investigation of other factors that affect the activity of the catalase, including, peradventure, temperature, pH, concentrations of substrate and enzyme and the presence of enzyme inhibitors.
Such experiments may at first sight seem quite straightforward, only as you try to translate your results you will be led into quite complex, just very interesting, aspects of chemic kinetics and reaction mechanisms.
Using an inorganic catalyst
Every bit an interesting dissimilarity, a similar increase in the rate of decomposition of hydrogen peroxide tin can be achieved using an inorganic catalyst such as manganese(IV) oxide or lead(lV) oxide.
You could ready out to look at how factors such as concentration of the peroxide, corporeality of the catalyst and temperature affect the rate of the decomposition. Experiments of this kind could lead you towards a possible reaction mechanism and towards the calculation of the activation free energy involved.
Contact lens chemistry
The catalytic decomposition of hydrogen peroxide will be very familiar to some students, as it is an integral function of i system for cleaning contact lenses. In this method the fifty eight December, 2008 make clean information technology and then the remaining solution is decomposed with the help of a platinum-coated catalyst. You lot might similar to investigate how the effectiveness of this goad changes nether unlike conditions and compare it with the other catalysts.
Monitoring the decomposition
At that place are several ways in which you can monitor the decomposition reaction. You might decide to follow the fall in concentration of the hydrogen peroxide. You tin can do this by taking samples of the reaction mixture at unlike times and running them into an acidified solution of potassium iodide. The iodine produced can be titrated with a solution of thiosulphate using starch indicator:
2H+ + HtwoOtwo + 2I– → I2 + 2H2O
I2 + 2StwoO3two– → 2I– + SfourO6 two–
The volume of thiosulphate solution required for the titration provides a measure of the corporeality of hydrogen peroxide in the reaction mixture at the different times. Every bit an alternative you might prefer to measure the volume of oxygen produced during the decomposition of the hydrogen peroxide. You tin can practice this by connecting a drinking glass gas syringe to a Buchner flask or Hirsch tube.
In that location is also another, more novel, approach to monitoring the enzyme-catalysed reaction which you might like to attempt. First, prepare a catalase excerpt. Next, use a file newspaper hole punch to stamp out circles from a filter paper. Soak one of these circles in the enzyme excerpt, drain, then apply a glass rod to poke it to the bottom of a exam tube containing the hydrogen peroxide solution. The bubbles of oxygen generated past the decomposition of the peroxide stick to the filter paper circle and carry it to the liquid surface. The time taken for this to happen provides a surprisingly authentic measure out of the relative activeness of the enzyme under unlike conditions.
Projection tips
- A catalase extract can easily be produced by macerating equal amounts of spud or other enzyme source with water in a nutrient processor or blender. Alternatively, you tin remove a cylinder of potato with a cork borer and slice off discs of equal thickness.
- 20 volume hydrogen peroxide is six% weight/volume or ane.8 mol dm-3. (Chlorine-free bleach works just besides!)
- 5 cmthree portions of partially decomposed 1 volume hydrogen peroxide tin be added to a mixture of four cm3 of 2 mol dm-3 sulphuric acid and 3 cm3 of ten% potassium iodide solution. Add ane drop of 3% ammonium molybdate solution and let the mixture correspond 2 minutes. Titrate the iodine released with 0.ane mol dm-3 sodium thiosulphate solution using 2 cm3 of ane% starch solution every bit indicator.
- A glass syringe sometimes sticks. You can minimise this problem by tapping it continually with a pencil.
- Platinum-coated discs are part of the 'Septicon' system for cleaning contact lenses. They are bachelor from Boots chemist shops.
The original article was written past Derek Denby. We are grateful to Derek for assuasive united states of america to reproduce information technology here.
This page is complimentary for your personal use, but the copyright remains with Philip Allan Updates. Please practice not re-create it or disseminate it in whatever fashion.
Chemistry Review is indebted to Don Ainley, who has helped to prepare this commodity for the Web.
Source: https://www.york.ac.uk/chemistry/schools/chemrev/projects/peroxide/
0 Response to "Odoes the Reactio N Occur Again When More Hydrogen Perxide Is Added"
Post a Comment