Edexcel A2 Chemistry: CH04 (09/06/14) and CH05 (17/06/14)

anybody know how to do arrenhius plot? I've seen multiple exam questions worth a lot of marks for it!

Are you referring to plotting lnk against 1/T to calculate the activation energy using the Arrhenius equation?

yep, any ideas

Well you'll always be given Arrhenius' equation as well as the value for R (8.31) so don't worry about that.
From what I've seen if it comes up (which I doubt it will as it came up June 2013), we'll be given data for k and T and potentially lnK and 1/T but we may have to work these out ourselves. Then you need to plot lnk against 1/T onto a graph using an appropriate scale (the graph has to cover at least half of the paper).

Once your points are drawn you need to calculate a line of best fit and then calculate the gradient. To calculate the gradient it's change in the y axis (which will be lnk) over change in the x axis (1/T).

The gradient = lnk/(1/T)
If we rearrange Arrhenius equation: lnk = -Ea/R x 1/T + constant
lnk/(1/T) = -Ea/R
Therefore lnk/(1/T) x R = -Ea
So our gradient x R = -Ea
gradient x 8.31 = -activation energy

Does this help? If so please let me know which aspect you're having trouble with and I'll try and explain it clearer or find some good resources.

No that helped a lot, I am just bad at rearranging the equations. To work out 1/T and lnK we will be given T and K etc. in a table though?

Thanks!

1.Apply a knowledge of the rate equations for the hydrolysis of
halogenoalkanes to deduce the mechanisms for primary and
tertiary halogenoalkane hydrolysis and to deduce the mechanism
for the reaction between propanone and iodine

2. Demonstrate that the mechanisms proposed for the hydrolysis
of halogenoalkanes are consistent with the experimentally
determined orders of reactions, and that a proposed mechanism
for the reaction between propanone and iodine is consistent with
the data from the experiment in 4.3e.

can someone help me on these four topics?i cant find or understand anything on these!:/

Is there any thread for unit 5?
if there is not one can someone please explain me this-

why Eo cell is not 1.33-0.41?

I don't think there is a unit 5 thread. I haven't done unit 5 since last year so excuse me if I'm bad at explaining.

Because in the full equation you're going from Cr3+ to Cr2O72- you need to reverse the equation (and hence the Ecell value) for Cr3+. So +1.33 becomes -1.33.

yah i got it!!i wrote the reverse eqn and wrote +1.33 V but it is supposed to be -1.33V! thanx!and aren't you sitting for any exam this june?

I've managed to compile every single question paper and make notes on everything that has come up since 2009; arranged into topics this should be easy to study from and get an idea of where you are/aren't picking up marks on each question.

There seems to be a repeat of most questions on every paper. Entropy and acid (buffer or titrations) calculations have come up on every single paper. Also the HCN mechanisms are used a lot for rate along with the iodine titration.

I will do the same for Unit 5 soon

Wow this is amazing! Thank you for posting.

I've managed to compile every single question paper and make notes on everything that has come up since 2009; arranged into topics this should be easy to study from and get an idea of where you are/aren't picking up marks on each question.

There seems to be a repeat of most questions on every paper. Entropy and acid (buffer or titrations) calculations have come up on every single paper. Also the HCN mechanisms are used a lot for rate along with the iodine titration.

I will do the same for Unit 5 soon