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1. Hey guys I'd appreiciate any help you could give me, I really need to do well in this and i'm rubbish and confused, so need lots of help ^_^;

Our investigation is 'the reaction between hydrogen peroxide and iodide ions'.
I have to carry out an experient to find the order of the reaction.
I'm adding set amounts of hydrogen peroxide, sulphuric acid, starch and sodium thiosulphate to a varied amount of potassium iodide + water.

First of all we need to do a table..... Yes, I was even stuck on that (I told you I was rubbish).
So far I have the basic table with all the amounts of stuff etc. But also I have the log of the volume of KI and 1/time and the log of the time.
Is that about all I need? Is it sensible to do 3 repeats of each run, or should I do more?

(Oh yeah, would any kind person like to explain the whole 1/time and log stuff and how to calculate them.... I really really don't understand this *points below*) I need to construct a graph to determine the order in respect to iodide ions.

'The rate simplifies to rate=k[I-]n or log(rate) = n log[I-] + constant
The rate can be represented as (1/time) and since the total volume in each experiment is constant, [I-] can be represented by the volume of KI, hence the rate becomes log(1/time) = n log (vol KI) + constant'

Also; how do you calculate the % difference between the value for the order you've got, and the correct value?

Thanks a lot for helping
2. (Original post by snivellus)

Hey guys I'd appreiciate any help you could give me, I really need to do well in this and i'm rubbish and confused, so need lots of help ^_^;

Our investigation is 'the reaction between hydrogen peroxide and iodide ions'.
I have to carry out an experient to find the order of the reaction.
I'm adding set amounts of hydrogen peroxide, sulphuric acid, starch and sodium thiosulphate to a varied amount of potassium iodide + water.
The Scottish Higher Chemistry PPA1 for Unit 1 is very similar and information on that can be found HERE

So far I have the basic table with all the amounts of stuff etc. But also I have the log of the volume of KI and 1/time and the log of the time.
Is that about all I need? Is it sensible to do 3 repeats of each run, or should I do more?
So, your headings for your table should (i think) be volume of KI, volume of water, concentration of KI (calculated using c=m/v), t1, t2..., average time and 1/t. As for the number of runs, i think three is sufficient but if you're wanting to be on the safe side, i'd go with five
1/time is the relative rate of reaction and is so that you can compare one rate to another regardless of type of experiment (i think )
This is just calculated by doing 1/time (where time is the time taken for the reaction to complete.

(Oh yeah, would any kind person like to explain the whole 1/time and log stuff and how to calculate them.... I really really don't understand this. I need to construct a graph to determine the order in respect to iodide ions.
I'm not too sure what you mean by the log stuff or the percentage difference.
As i said above, 1/time is just 1/time taken for reaction to occur. Not sure what you mean about the log stuff though sorry!

Sorry i couldnt be of any more help,
Nathan
3. (Original post by snivellus)

Hey guys I'd appreiciate any help you could give me, I really need to do well in this and i'm rubbish and confused, so need lots of help ^_^;

Our investigation is 'the reaction between hydrogen peroxide and iodide ions'.
I have to carry out an experient to find the order of the reaction.
I'm adding set amounts of hydrogen peroxide, sulphuric acid, starch and sodium thiosulphate to a varied amount of potassium iodide + water.

First of all we need to do a table..... Yes, I was even stuck on that (I told you I was rubbish).
So far I have the basic table with all the amounts of stuff etc. But also I have the log of the volume of KI and 1/time and the log of the time.
Is that about all I need? Is it sensible to do 3 repeats of each run, or should I do more?

(Oh yeah, would any kind person like to explain the whole 1/time and log stuff and how to calculate them.... I really really don't understand this *points below*) I need to construct a graph to determine the order in respect to iodide ions.

'The rate simplifies to rate=k[I-]n or log(rate) = n log[I-] + constant
The rate can be represented as (1/time) and since the total volume in each experiment is constant, [I-] can be represented by the volume of KI, hence the rate becomes log(1/time) = n log (vol KI) + constant'

Also; how do you calculate the % difference between the value for the order you've got, and the correct value?

Thanks a lot for helping

Doing the exact same one!! But my chem teacher told us not to worry about all the log stuff just yet, that's going to come later on. So al we had to do in lesson was plan the experiment out and know what we're doing as the practical is on tuesday and were going to be examined on it!!!

The graphs you're on about, draw it and just re arrange the line equation y=mx+c into rate=[Z]*n and then to log rate=n log [Z]

The you can plot the new graph using the equation and draw another graph with headings log rate(y-axis) and log [Z] (x- axis) take the gradient and that is equal to n,the order of reaction.

Hope that makes some sense! Btw the table I decided to do a really simple one just time(sec) and experiment number (as there are 5) as my headings, and 3 soinds more than enough, i never get to do more than 2!

Good Luck!
4. We did a similar one with peroxydisulphate instead of hydrogen peroxide.

Time
logTime (get from calculator, press log and then the time)
Temperature (in kelvin)
1/Temperature

We used our graph to find the activation energy (Ea), though, so I'm not sure how a graph of logTime against 1/T would be to find the order, although it is in my notes....which are in my locker at school

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Updated: January 28, 2006
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