Chemistry - its that time of year again

[tris-]

so its now that time of year again where i tack teh chemistry coursework.

for all who helped last time - cheers. i got an A.

this time its a different kettle of fish. im fairly confident im correct but i have nothing to compare it to back it up/

A reaction first order with respect to A and second order with respect to B

imo -

k[A]

a reaction third order with respect to A, second order with respect to B and zero order with respect to C

imo -

k[C][A]

i see the acronym does spell cant be arsed aswell.

fantastic, because thats how i feel at the min.

but anywayyy, anyone care to correct me if im wrong?

 

[Lamp]

Not too sure about that

But I am familiar with the chemistry of beer on the taste buds.

Why don't you pop down to your local for some inspiration

 

[tris-]

that would be excellent idea if it wasnt already teh plan for this evening. as it is i have a chem coursework and 2 lab experiments that need some hardcore work ;/

 

[tris-]

no one knows then?

;/

 

[Marc]

Wikipedia rocks

http://en.wikipedia.org/wiki/Reaction_rate

Bit over my head, but it does back up what you want confirming

 

[Marc]

Where C (your post) = T (in wikipedia) i guess?

 

[tris-]

im not sure what that T is. its in () brackets instead of [] ones.

cheers though

 

[Marc]

ahh yes, didnt see that.

 

[Rinusch]

Could you specify what [C] is supposed to compose?
as far as i can remember:

Rate = k [a]
in which:
k= Constant value affected by enviromental factors (temp. and UV radiation (sunlight!) etc)
[a] Nucleophile
Electrophile (last two can be switched though)

But im only 2nd year uni, so i could be rather wrong here

(did get 86% score out of that exam though )

 

[Stanny]

lol, what level is this chem?

 

[tris-]

rinusch

no propery is specified.

they simply are letters

 

[old.windforce]

i got a master degree in organic chemistry but no fucking clue what you are talking about

 

[tris-]

i am talking about A level chemistry - rates of reaction

 

[Rinusch]

this formula simply specifies the rate on which a reaction will take place, due to an unpredictable k, one can not calculate it on forehand, but a rough estimation can be made, giving you indications wether it will work or not, if you for example need to heat the solution.

its pretty usefull when building a homebrew synthesis

but back on topic: If [C] is still a free marker,. wouldnt that suppose interraction of the solvent? (like ether bridges in organometallic halides)
a good example of this is the use of Tetrahydrofuran in Grignard reactions. the ether has a important influence on the formation of the reagent and thus on the speed of the reaction.
its basically the only thing i can think about due to the fact that 3 components react in a sequence to eachother (correct me if im wrong here though, could well be mistaken)

 

[tris-]

rinusch. forget about them having any property. i dont even want to work out what K. what i am trying to ask is, have i written the order down correctly.

hell just forget they are chemicals, they are simply letters. and you are being asked to put letters in the following order

-
a reaction third order with respect to A, second order with respect to B and zero order with respect to C
-

 

[Rinusch]

rinusch. forget about them having any property. i dont even want to work out what K. what i am trying to ask is, have i written the order down correctly.

hell just forget they are chemicals, they are simply letters. and you are being asked to put letters in the following order

-
a reaction third order with respect to A, second order with respect to B and zero order with respect to C
-

I asume that would indeed be correct, in which wouldnt have any influence at all it would indeed be 0 order.

though i cant find any reference to this @ all. logically it should be correct

 

[Megarevs]

im not sure what that T is. its in () brackets instead of [] ones.

cheers though

isnt that the temperature in kelvin? :>

In this equation k(T) is the reaction rate coefficient or rate constant, although it is not really a constant, because it includes everything that affects reaction rate outside concentration: mainly temperature but also ionic strength or light irradiation.

 

[tris-]

I asume that would indeed be correct, in which wouldnt have any influence at all it would indeed be 0 order.

though i cant find any reference to this @ all. logically it should be correct

so you reckon this is correct


k[C][A]

 

[Rinusch]

so you reckon this is correct


k[C][A]

It seems logically correct, however im not aware of it excisting. doesnt seem likely to be a 3rd party in a reaction namely. (see my above post). im not gonna say its true till i have seen the formula in some textbook ^^.

 

[tris-]

i doubt you will find it. since the tutor just made up for a question.

it doesnt matter if it excists or not. what matters is that the order i have written is the same as asked in the sentance.

 

[Agrigo]

Have it all in teh lab manual at zee house , will put up all the rates and so on when back at the house =]


(and yes i don't remember it , im one of those "get everything in your head for the exam then forget it 5 mins after" people)

 

[tris-]

thanks agrio. im fairly sure though you wont find this in a book. the tutor has just made it up for a question.

 

[Achilles]

Hi there. Chemistry unit 5 kinetics is like playing alb no? teh hardmode!! All i have to say isnt a second order reaction: k[...]^2 and a zeroth order reaction: k[...]^0, therefore= k. Dont really understand the question. Only took notes on this on Fri, so please dont mock me if im being stupid ;p.

 

[Agrigo]

Went home and it went like this :
1) Throw bag on bed
2) Went to locker
3) Realise that after the exam i burned the notes
4) Sleep
5) wan .................. wait a min , you dont need to know that part

Sorry to not be any help , hope you find it out soon mate =)

 

[Rinusch]

I have been giving it some X-tra thought, but if a tutor made it up, couldnt the answer be as simple as: [C] is the 3rd component in the equation, therefore the "third" Order? seems to damn easy though, but doesnt seem unreasondable, since it demands understanding of the [A] and terms in the equation and thus understanding of the formula

 

[tris-]

rinusch thats what i mean.

i know the powers of all the components need to equal what order of reaction it is.

like a 2nd order.

it would be a^2 or a^1 b^1

etc

 

[Rinusch]

rinusch thats what i mean.

i know the powers of all the components need to equal what order of reaction it is.

like a 2nd order.

it would be a^2 or a^1 b^1

etc

Seeing this and the above listed information, it could aswell be the 3rd order or the zero-order in general, basically saying that either of us could be right here, but if [C] would be zero order it would always be 1 and have no influence on the equation, for C^0 = 1 and would have no influence what so ever, therefore 3r order seems more logic

 

[rayzor]

with ^ meaning "to the power of" (cant find superscript )

A reaction first order with respect to A and second order with respect to B

imo -

k[A]

i think it should be k[A]^2
( cos k[A] is the same as k[A] )

a reaction third order with respect to A, second order with respect to B and zero order with respect to C

imo -

k[C][A]

similiarly, i think this should be: k[A]^3^2[C]^0

anything ^0 = 1, so answer is k[A]^3^2

( again k[A][C] is the same as k[C][A] etc ) the second order/third order stuff doesnt describe the position in the equation, but the power of [X] )


hope this helps, and is right, been a long time since i did physical chem

 

[tris-]

doesnt that make the second one a 5th order reaction then?

i cant find them existing anywhere on google.

 

[rayzor]

doesnt that make the second one a 5th order reaction then?

it makes it a 5th order reaction over all, so yes.


/edit: found this: http://www.chemguide.co.uk/physical/basicrates/orders.html#top

explains it all nicely imo.