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Topic: Reaction rate conversions?  (Read 258 times)

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Offline HoneyDumplings

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Reaction rate conversions?
« on: February 22, 2021, 05:33:12 PM »
Is there any way to deduce the ending concentration and the reaction rate of a reactant if you know the equation, that it is a first-order reaction, the starting concentration for the reactant and product, the ending concentration of the product, and the rate of reaction of the product?
I feel like there is a way... but I can't think of it. Any help would be appreciated!!!

Offline HoneyDumplings

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Re: Reaction rate conversions?
« Reply #1 on: February 22, 2021, 06:09:28 PM »
Really what I want to know is that is there any way to find the rate constant for a reaction that I did with a gas pressure sensor? I know the change in pressure, and I know you can do p/RT=n/v which is concentration but I don't know where to go from here... is it possible?

Offline Meter

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Re: Reaction rate conversions?
« Reply #2 on: February 23, 2021, 04:28:28 AM »
Can you write out the reaction?

Offline HoneyDumplings

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Re: Reaction rate conversions?
« Reply #3 on: February 23, 2021, 05:11:53 PM »
Can you write out the reaction?

The decomposition of hydrogen peroxide in the presence of a Maganese IV oxide catalyst.
2H2O2  :rarrow:  O2 + 2H2
      MnO2


Offline HoneyDumplings

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Re: Reaction rate conversions?
« Reply #4 on: February 24, 2021, 08:41:38 AM »
The reaction was done at 30 40 50 60 and 70 degrees C if that helps as well. I have thought about the 1:2 ratio of the oxygen to hydrogen peroxide but would the rate for hydrogen peroxide be just double the rate of oxygen? 

𝑅 = 𝑘 [H2O2 ]
And to my understanding to find k I would divide the rate of reaction by the final concentration of hydrogen peroxide? Is there any way for me to find that knowing the rate for oxygen from p/(rT)=n/v  per second?

Offline Borek

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Re: Reaction rate conversions?
« Reply #5 on: February 24, 2021, 01:13:57 PM »
Is there any way to deduce the ending concentration (...) of a reactant if you know the equation (...) the starting concentration for the reactant and product, the ending concentration of the product

Sounds like a simple stoichiometry.
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Offline HoneyDumplings

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Re: Reaction rate conversions?
« Reply #6 on: February 24, 2021, 01:24:06 PM »
Is there any way to deduce the ending concentration (...) of a reactant if you know the equation (...) the ending concentration of the product

Sounds like a simple stoichiometry.

Is the rate for hydrogen peroxide just double that of oxygen? Do you include the manganese iv oxide in the rate constant equation or will the rate constant just be the ending concentration of hydrogen peroxide divided by the rate of disappearance of hydrogen peroxide (x2 that of oxygen?) and would p/rt=n/v divided by seconds be the rate of reaction for oxygen?

I know it is simple but I have really confused myself with all this  :-\

Offline Borek

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Re: Reaction rate conversions?
« Reply #7 on: February 25, 2021, 03:09:16 AM »
You are mixing rates (kinetics) with final amount (equilibrium) - these are two separate problems, so it is difficult to say what you are really after.

Yes, the rates of consumption/production of different substances taking part in the simple reaction are related by their stoichiometry coefficients.

Amount of MnO2 matters, but it was constant during the experiment so you don't have data to determine the dependence. It will be just part of the k.

Finding rate is best done by fitting the amounts of substance (doesn't matter which one) at known time points to the reaction curve. Just initial and final concentrations are not enough.
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Offline HoneyDumplings

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Re: Reaction rate conversions?
« Reply #8 on: February 25, 2021, 07:52:24 AM »
You are mixing rates (kinetics) with final amount (equilibrium) - these are two separate problems, so it is difficult to say what you are really after.

Yes, the rates of consumption/production of different substances taking part in the simple reaction are related by their stoichiometry coefficients.

Amount of MnO2 matters, but it was constant during the experiment so you don't have data to determine the dependence. It will be just part of the k.

Finding rate is best done by fitting the amounts of substance (doesn't matter which one) at known time points to the reaction curve. Just initial and final concentrations are not enough.


I have the change in pressure over time at different temperatures and I am trying to find the rate constant so I can do an Arrhenius graph to find activation energy. Is it possible or have I confused myself so much. what concentration do I need for the rate constant equation?

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