Chemistry Salters Investigation

Hi, it's a bit of a long winded one but i am trying to write up my investigation- i did the decomposition of hydrogen peroxide in the presence of inorganic transition metal catalysts. I have found the order of reaction etc and varied the temperature at which i carried out the experiment. Does anybody know how to calculate rate constant k using the arrhenius equation?

Reply 1

Borek

Are you sure you are not mistaking something? You can use Arrhenius equation to find activation energy, once you know rate constant - but rate constant you have to find from the experimental data.

Unless you were given activation energy separately, which I doubt.

Reply 2

mynameischloe

Original post by Borek

I think i am supposed to calculate k first but am unsure how to do this from my experimental data? I then have to use k and arrhenius to calculate activation enthalpy :s-smilie:

Reply 3

dragonkeeper999

Original post by mynameischloe

I think i am supposed to calculate k first but am unsure how to do this from my experimental data? I then have to use k and arrhenius to calculate activation enthalpy :s-smilie:

I assume that you varied the concentration of each reactant in your experiments. This allows you to calculate k using the rate equation for your reaction. You can then use this value of k to calculate the activation enthalpy using the Arrhenius equation and your data from the temperature experiments :smile:

Reply 4

Borek

What kind of data have you collected?

Reply 5

mynameischloe

Original post by dragonkeeper999

Yes i did, thankyou! Going to have a good crack at it now

Reply 6

mynameischloe

Original post by Borek

What kind of data have you collected?

I tested 5 different concentrations of hydrogen peroxide keeping catalyst concentration constant. I then tested 5 different amounts of manganese (IV) oxide keeping H2O2 constant. I worked out the initial rates of these reactions and the order is first in respect to both reactants.

Reply 7

Borek

Original post by mynameischloe

Does anybody know how to calculate rate constant k using the arrhenius equation?

Original post by mynameischloe

I worked out the initial rates of these reactions

If you have the initial rate and you know the initial concentration, you already have the rate constant? If so, why do you want to calculate it from Arrhenius equation?

Or is it irrelevant now, as you got it after dragonkeeper999 hints?

Reply 8

itsije

Original post by mynameischloe

How did you vary the concentrations of Hydrogen Peroxide? I've looked almost everywhere for info and I'm still confused :s-smilie:

Reply 9

mynameischloe

Original post by itsije

How did you vary the concentrations of Hydrogen Peroxide? I've looked almost everywhere for info and I'm still confused :s-smilie:

Hi, sorry for the very late reply! I just diluted down the standard 100vol hydrogen peroxide which they provided at school to get the concentrations I needed. I tested 0.2 0.4 0.6 0.8 and 1molar.

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Reply 10

itsije

Original post by mynameischloe

Thank You

Reply 11

lux_09

What method did you use to measure the decomposition of hydrogen peroxide?

I used a gas syringe

I'm also doing this same experiment, I'm using manganese (IV) oxide as my catalyst. How did you work out the order of reaction?

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Reply 14

itsije

I used yeast as a catalyst and I had a first order reaction

Reply 15

peachy13

That's what I expect mine to be but how do I work out out from the data I have. I have done 5 experiments varying the concentration of h2o2. 5 experiments varying the amount of mno2. I'm currently doing experiments with varying temperature.