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Zinc Acid Reaction - Rates of reaction - OCR B Salters C/W

Hello I desperately need some help/guidiance, if anyone has done this experiment your help would be highly valued! Basically I had to react Zinc with Sulfuric Acid(@3 different concentrations)...which goes on to produce Zinc Sulfate and Hydrogen. I then added Copper Sulfate(@3 different concentrations) to see how this catalysed the reaction, after doing this I drew initial rate against concentrations for the experiments with the Sulfuric acid and Copper Sulfate. However I need to calculate rates to find k (constant) I can do this but I do not know what to talk about and how this is related to the arrhenius equation, Im a tad confused and hope somebody could fill me in!
Reply 1
Avatar for shengoc
shengoc
12
I am just wondering if you do the experiments at different temperature to get the rate or value of k at specific temperature.

arrhenius equation states

k = Aexp(-E/RT)

lnK = lnA - E/RT

you plot a graph of lnK vs 1/T which gives you a gradient of -E/R and y-intercept of lnA
Reply 2
Avatar for jazz=)
jazz=)
OP
Im pretty sure the y axis is ln (k) and yep the gradient is -Ea/R btw i did how long it took for my gas to reach xcm^3 @ different temperatures. Once I've worked out Ea what am I supposed to do? I've done that but I have 2 diff rate equations(one 4 the reaction with h2so4 and the other with cuso4 at diff concentrations) Basically what Im trying to ask is what do i do/say about the arrhenius equations and the rate equations...do they link?
Reply 3
Avatar for shengoc
shengoc
12
Original post by jazz=)
Im pretty sure the y axis is ln (k) and yep the gradient is -Ea/R btw i did how long it took for my gas to reach xcm^3 @ different temperatures. Once I've worked out Ea what am I supposed to do? I've done that but I have 2 diff rate equations(one 4 the reaction with h2so4 and the other with cuso4 at diff concentrations) Basically what Im trying to ask is what do i do/say about the arrhenius equations and the rate equations...do they link?


when you do the set of experiments at different temperatures, all the other variables(ie concentrations of your reactants) should be the same. ie only one quantity changes

ie rate = k [A]^a ^b

but if [A] and is the same for all set of experiments at different T, they would be constant it would be like

rate = k * constant

only k changes then with temperature.

the second set of experiment deals with the catalyst loading. so here, at a single temperature, you are varying the concentration of catalyst to see if there is a change in rate.
if there is, your catalyst has a role in your rate equation - you can work the order by using your sets of data to plot some graphs
if there isn't, your catalyst is zero order w.r.t. your rate equation.
Reply 4
Avatar for jazz=)
jazz=)
OP
Hmm so do I just work out k from the rate equations I have..then see what k is in the arrhenius equation? I think i get what you said, sooo if k is higher in the arrhenius equation that means the catalyst was effective, right? :smile:
Reply 5
Avatar for jazz=)
jazz=)
OP
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