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Topic: Affect of temperature on Daniel Cell and activation energies  (Read 3867 times)

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JustGeoff

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Affect of temperature on Daniel Cell and activation energies
« on: August 25, 2005, 07:07:59 AM »
I'm working on a rather large Chemistry project where I ran a variant of the daniel cell (two half cells, and instead of using zinc sulfate I had to use zinc chloride) at different temperatures and then measured the current .

I know that from current I can find out the amount of electrons per second being transfered, which I means I can figure out the amount of moles of zinc being removed from the zinc electrode, and that should be the same as the number of moles of copper which form on the copper electrode.

But what I am trying to do at this point is firstly calculate the activation energy fo the reaction (I believe the value I get should be the lower activation energy of either of the two half cells). I know that you can use the equation rate = k[A] (I don't think I need to worry about orders of reaction because I used one molar solutions) to find k (because I know the rate) which I can then use to draw a Arrhenius plot to find the activation energy.

But I don't know if that equation works when you are dealing with a solid reacting with a liquid, or how it would work if it would. Can someone help me out with this, please?

Also I wonder if there is anyway for me to get a literary value for some of these numbers, like the rate of reaction, the activation energy ect. I'd like to be able to compare the answers I got with true values in my write up.

Thanks.

*edited to improve ease of reading
« Last Edit: August 25, 2005, 03:52:05 PM by geodome »

Offline Donaldson Tan

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Re:Affect of temperature on Daniel Cell and activation energies
« Reply #1 on: August 25, 2005, 03:59:13 PM »
But what I am trying to do at this point is firstly calculate the activation energy fo the reaction (I believe the value I get should be the lower activation energy of either of the two half cells). I know that you can use the equation rate = k[A] (I don't think I need to worry about orders of reaction because I used one molar solutions) to find k (because I know the rate) which I can then use to draw a Arrhenius plot to find the activation energy.

But I don't know if that equation works when you are dealing with a solid reacting with a liquid, or how it would work if it would. Can someone help me out with this, please?

the concentration of the solid is effectively its density, and the density hardly varies with temperature. however, the concentration of the active ingredient in your electrolyte might change because it is being consumed.

In another words, the rate equation excludes any term involving the solid.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

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