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# calculate activation energy for the decomposition of hydrogen peroxide watch

1. Need some help.
I need to calculate the activation energy for the decomposition of hydrogen peroxide into oxygen and water, catalyzed by Manganese dioxide. I measure the volume of the gas evolved.
Then i would change the catalyst to lets say Lead(II) Oxide and then i would compare the activation enthalpies.

How would i work out the activation enthalpy.. is there a equation i require? From what data would the activation enthalpy be derived from?

Please some one help me. Any one at all, no matter how small the info is.
2. Google the Arrhenius equation. If you have worked out your rate constants for at least two different temperatures you can use them to work out the activation energy of the reaction. If you need more help do ask.
3. (Original post by Blocker)
Google the Arrhenius equation. If you have worked out your rate constants for at least two different temperatures you can use them to work out the activation energy of the reaction. If you need more help do ask.
The Arrhenius equation.. thanks for that

But the thing is that i carried the experiment out at room temperature so how i will input temperature??
4. If at room temperature then you can probably just assume 298K.

If you want to calculate activation energy however, you'll need more data at different temperatures. In this case you might do something at 308K or 288K by using a water bath to control the temperature of your system.

It is impossible to calculate the activation energy for a process with only kinetic data at just one temperature.
5. (Original post by Blocker)
If at room temperature then you can probably just assume 298K.

If you want to calculate activation energy however, you'll need more data at different temperatures. In this case you might do something at 308K or 288K by using a water bath to control the temperature of your system.

It is impossible to calculate the activation energy for a process with only kinetic data at just one temperature.
So if i place the hydrogen peroxide in a water bath at a totally different temperature(so far Ive been doing room) and then make it react with the catalyst and observe how much oxygen is evolved then it'll be possible for me to calculate the activation enthalpy. Then for more observations i could do another temperature(e.g add 10 c) and then use the Arrhenius equation?
6. Indeed. 2 temperatures is enough, but for an accurate result you want at least 3 or 4. More than that is probably more time than you need to put in at A level. Use the same procedure as before with your different temperature systems to calculate the orders and rate of reaction (the order should be unchanged but its always worth checking!), then use your different rate constants and temperatures to calculate the activation energy and Arrhenius constant (A in the Arrhenius equation) and report them. After that your onto error analysis :P

A water bath is definetly the best way to do that. Bear in mind that the reaction might be quite strongly dependant on temperature and if you increase it too much may become too fast to follow. On the other hand, the further apart your temperature steps, the more accurate your results. It may be worth checking the temperature of your original data: although room temperature is defined as 298K most labs ive been in tend to be a bit colder. Grab a thermometer and read it next time your in the same room.

[EDIT] Between 5 and 10 degree steps sounds about right. Good luck!

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