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GAL-actic
08-01-08, 03:39 PM
I had to calculate the reaction rate constant of ethanol, propanol and methylpropanol and compare these values with the theoretical values, but I can't find those values anywhere. I think it depends on the reaction.

Anyway these are my calculated reaction rate constants:

ethanol: 0.609
n-propanol: 0.509
methylpropanol: 0.712

Does anyone know where I can find the theoretical values or how I can determine/calculate the RRC's???
Mace
08-01-08, 04:42 PM
I don't completely understand the question.

For what reaction are you trying to calculate the rate constant?
Mace
08-01-08, 04:53 PM
To answer your question, the reaction rate constant is a property of a particular reaction and it does vary by temperature.
GAL-actic
08-01-08, 06:01 PM
It's about an oxidation reaction of alcohols with chrome acid to make ketons and aldehydes.

3RCh2OH + 2H2CrO4 + 6H3 ---> 3RC(O)H + 2Cr (3+) + 14 H2O

the ratedetermening part. reaction with excess of alcohol is:

RCH2OCrO2OH + H2O--> RC(O)H + H3O + HCrO3

alcoholsolutions:
- 1,0 M in H2O for ethanol and n-propanol
- 0.5 M in H2O for 2-methylpropanol

I hope this will help
GAL-actic
08-01-08, 06:41 PM
To answer your question, the reaction rate constant is a property of a particular reaction and it does vary by temperature.

Temp is 35C
Mace
08-01-08, 10:00 PM
OK, and the rates that you calculated, are they from observation in the lab?
GAL-actic
08-01-08, 10:05 PM
OK, and the rates that you calculated, are they from observation in the lab?

yup

I used this formula:

ln A (t)=ln A (0)-kt

A is the extinction
Mace
08-01-08, 10:17 PM
yup

I used this formula:

ln A (t)=ln A (0)-kt

A is the extinction

OK, my chemistry is a bit fuzzy. (I'm an old man).

But the only way I know how to calculate this is exactly how you did it, by observation.

So I'm trying to figure out what they mean by "compare to theoretical values"....

Still thinking...

Can you copy/paste the entire question from the problem set or exam or whatever this is?
Sulaiman Harun
08-01-08, 10:19 PM
:start:

:salams

Sister, I found this website and specifically this link about Chrome Acid:
http://mrw.interscience.wiley.com/eros/articles/rc164/frame.html

Maybe this might be just helpful but you've got to register there before you can view articles
GAL-actic
08-01-08, 10:32 PM
OK, my chemistry is a bit fuzzy. (I'm an old man).

But the only way I know how to calculate this is exactly how you did it, by observation.

So I'm trying to figure out what they mean by "compare to theoretical values"....

Still thinking...

Can you copy/paste the entire question from the problem set or exam or whatever this is?

It's in Dutch lol. I translated that part. I think they mean by "compare to theoretical values" that you have to calculate the reaction rate constant by using this formula:

Concentration change/time change=rate

I'm not sure

but then I don't know which concentrations to use
GAL-actic
08-01-08, 10:33 PM
:start:

:salams

Sister, I found this website and specifically this link about Chrome Acid:
http://mrw.interscience.wiley.com/eros/articles/rc164/frame.html

Maybe this might be just helpful but you've got to register there before you can view articles

Will have a look at it. :jkk:
GAL-actic
09-01-08, 06:23 PM
Somebody? Anybody?

Still haven't found out about this one
Mace
09-01-08, 11:08 PM
Somebody? Anybody?

Still haven't found out about this one

I asked my wife about this today and she couldn't recall any way to calculate this other than empirically, which you've already done.

Unless, she said, you are doing a differential analysis between two known temperatures. Then you could calculate the expected rate at temp B given the rate at temp A. And then compare that to the observed rates.

She asked the same thing I did, which is "let me see the question as stated in the problem set."

But being as we can't read Dutch, that's tough.

Sorry we couldn't be of more help. I hope you will post the solution here when you find it. I'm curious to learn what it is.
GAL-actic
09-01-08, 11:19 PM
I asked my wife about this today and she couldn't recall any way to calculate this other than empirically, which you've already done.

Unless, she said, you are doing a differential analysis between two known temperatures. Then you could calculate the expected rate at temp B given the rate at temp A. And then compare that to the observed rates.

She asked the same thing I did, which is "let me see the question as stated in the problem set."

But being as we can't read Dutch, that's tough.

Sorry we couldn't be of more help. I hope you will post the solution here when you find it. I'm curious to learn what it is.

I understand and thank you very much.

I'm gonna ask about it tomorrow and hopefully have the answer then. I'll let you know.
GAL-actic
29-02-08, 07:56 AM
I haven't asked yet, I'm really sorry. I've tried but this teacher isn't always present.


I'm doing placement right now; Organometal chemistry. Anyone familiar with it?
Ibn Al-Jarrah
29-02-08, 08:43 AM
ur doing a level?:rubeyes:
GAL-actic
29-02-08, 09:42 AM
ur doing a level?:rubeyes:

I think it's abit different here.
Ibn Al-Jarrah
29-02-08, 09:48 AM
I think it's abit different here.

why where are you? over here A level is the year before university
GAL-actic
29-02-08, 11:46 AM
why where are you? over here A level is the year before university

The Netherlands lol

ah okay ...no then I've done that some years ago.
GAL-actic
29-02-08, 06:48 PM
Is A levels only used in UK or also in USA?
Ibn Al-Jarrah
29-02-08, 06:57 PM
USA have a weird system of education where college comes before high school or something:wacko:
GAL-actic
29-02-08, 07:02 PM
I see:confused:
Ibn Al-Jarrah
29-02-08, 07:10 PM
I see:confused:

they take everything english, mess about with it, change the spelling...

England:
year 1-6 primary school
7-11 secondary (high) school (GCSE)
12-13 college/6th form ( a levels)
14-17/18 university (degree)

US: duno
Mace
29-02-08, 08:06 PM
USA have a weird system of education where college comes before high school or something:wacko:

We finish high school and then go to what we call "college" or "university". Typically this is around age 18, but some go earlier or later of course.

Colleges for us are either small schools (too small or too focused to be considered a university) or a particular faculty within a university (e.g. the college of whatever within the university of such and such)

But in normal speaking whether we are going to a small college or a huge university we still say we're going to college. So I may say "my son is graduating from high school in 2010 and so we need to plan for him moving to college in Sept 2010." And that's how we would say it whether he goes to some small community college or (hopefully in his case) a major university.
GAL-actic
29-02-08, 08:15 PM
We finish high school and then go to what we call "college" or "university". Typically this is around age 18, but some go earlier or later of course.

Colleges for us are either small schools (too small or too focused to be considered a university) or a particular faculty within a university (e.g. the college of whatever within the university of such and such)

But in normal speaking whether we are going to a small college or a huge university we still say we're going to college. So I may say "my son is graduating from high school in 2010 and so we need to plan for him moving to college in Sept 2010." And that's how we would say it whether he goes to some small community college or (hopefully in his case) a major university.

I think that's pretty close to the system used in the Netherlands. And I thought I was confused:)