Practical investigations
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Why is hydrogen peroxide kept in the refrigerator??? Also help me design and experiment to explain why?????????/
Corrie writes .....
Hydrogen peroxide is unstable and decomposes slowly into water and oxygen gas - more quickly in the presence of a catalyst.
You could show this by determining the concentration of hydrogen peroxide in a sample stored in refrigerator for a while with some of the same sample stored in a warm room - this may need to be for several days to obtain a noticeable difference.
There are various ways of determing the concentration of hydrogen peroxide in solution. Here is the answer to a previous question on this subject. You may find more if you use the the FAQ Search facility on React.
Potassium permanganate - now more commonly known as potassium manganate(VII) - reacts with acidified hydrogen peroxide. Assuming that the acid chosen is sulphuric acid the reaction is:
2KMnO4 + 3H2SO4 + 5H2O4 -> K2SO4 + 2MnSO4 + 8H2O + 5O2
Given that the potassium manganate(VII) is a self-indicator, the procedure used is therefore a titration. Pipette a known volume of your hydrogen peroxide into a conical flask, add an excess of dilute sulphuric acid, and titrate with the 0.02 mol dm-3 potassium manganate(VII). Oxygen will be evolved during the titration, and the end–point is signified when one drop of the manganate(VII) solution causes the mixture to remain faint pink, even after shaking. Using the equation above, the concentration of the hydrogen peroxide can then be calculated.
Always carry out a risk assessment and check with your teacher before carrying out any practical work.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
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updated: 17 April 2007
