IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

PRAT33

CAN THE ORDER OF A REACTION BE GREATER THAN 3?

nishant

obviously,it can be...if more than 3 reactants are taking part to form products or if two reactants are having 2 moles each,then order can be greater than 3..

coolyog

yes it can be greater

PRAT33

I AM TALKING OF ORDER NOT MOLECULARITY

ALSO O P TANDON HAS GIVEN THAT EVEN MOLECULARITY CANNOT EXCEED 3(VERY RARELY IT DOES BUT VERY RARELY)

vinay007

order of reaction is greater than 3 or upto n th term or it can be any rational(p/q) no.

Lolita

Yes it can be.

dinesh_ddt

hey order can be ne rational thing as said by vinay007 but molecularity is rarely less than three coz the probability of 3 reacting species coming together simultaneously to form the product is almost zero....!!!!

arun-rashi

ya it can be because if concentration of more than three molecule decide rate of reaction order of reaction is greater than 3.but remember that moleculerity express effective collision between molecule so it cannot be greater than 3,if there is known as psuedo moleculerity.

abhay_yadav80

yes, order of a reaction can be greater than 3
order of a reaction is determined by experimental values,and can be greater than 3 for reactants.
but molecularity of a reation cannot be gerater than 4 .
for more detail reply me and rate me....

rintu

No.
See there is no theoritical restriction on the order not being greater than 3.
But practically till date no reaction has been seen where the order is greater than 3.

People here are confusing order with molecularity.

Order is the summed power of the concentration terms as defined in the rate expression of a particular reaction and it has simply nothing to do with the reactants.

Never think that a reaction :: A + B ----> R + S will have a rate equation like
(-rA) = Rate of decomposition of A
(-rA) = k [A] [B]......(1)...But it can anytime be (-rA) = k [A]^0.5........(2)
or even (-rA) = k [A] [R] [S].......(3)....The rate equation is a purely experimental one and never can be predicted theoritically.
Only "ELEMENTARY EQUATIONS" are those who have their respective powers in the rate equation equal to their stoitiometric coefficients in the reaction. Like if the equation given by me is ONLY an elementary reation then ONLY rate expression (1) is suitable otherwise you need to find the rate expression experimentally and then find out the order. There are different techniques tofind out order experimentally like using
DIFFERENTIAL and INTEGRAL techniques, you need not concern them right now. So donot confuse Rate expression concentration powers with stoitiometric coefficients. So if number of reactants is more than 3 Then only for an ELEMENTARY REACTION the order can be greater than 3. But very
sadly in this world till date no such ELEMENTARY EQUATION exist.

So, to be concise ORDER greater than 3 has not been found till date. And remeber that you cannot dictate the order of the reaction by merely seeing the reaction. It can only be done so for ELEMENTARY REACTIONS. Otherwise it need to be purely found out experimentally.

rintu

Actually this answer on kinetics is posted by my elder brother Debabrata Nag who is currently Pursuing Chemical Engineering at Jadavpur University, Kolkata. And Chemical Reaction Enginnering that comprises all these things are his most prior interest.

arsenal2007

it can be grater than 3 but very very rarely

Ask & Discuss Questions with Community & Experts