reactant molecules so that becomes equal to thresholad value.

Activation energy = threshold energy -avg. K.E. of reactant molecules

Activation energy = threshhold energy - avg ke of reactant molecule A - A + B - B diagram2AB

Arrehevius eqn



taking log on both sides

lnk=ln^A

Letvalue of rate constant at temp t1&t2 are k1 &k2 respectively

lnk1=lnA

lnk2=lnA

(iv)-(iii)

lnk3-lnk1















on solves

E_a=44.13kjmol^-1



Easy type:-



Q.1 for rxn 2NO₂+F₂2N0₂F

exp. rate law is r=kNO₂ Propose mechanism Of RXN

ANS:- RATE = K[NO₂][F₂] Implies that slow step

of rxn involves only one molecule of each reacting species so, mechanism.

NO₂+F₂NO₂F + F

NO₂+F₂NO₂ F

Over all rxn is 2NO₂+F₂2NO₂

Q 2:- Given that temp coeff for sponification of ch₃cooc₂h₅

by NAOH is 1.75. calculate activation energy?

Dumb question:-



Q : what is temp coeff?

Ans:- it is rate of constant at 35c to 25c

given,

2.303 log₁₀

2.303 log₁₀

Ea = 10.207kcal/mol Q.3:- A hydrogenation rxn. is carries out at 500k. if some

rxn. is carried out in presence of catalyst at same rat, temp. required is 400k.

calculate activation energy if catalyst lowers activation energy berrier by

20kj/mol Ans.:- let Ea & Ea' be energy of activation is presence of catalyst

for hydrogenation rxn,; then k= A_e^{-Ea / RT}

inpresence of catalyst, k1=A_e^{-Ea/ (rx500)}

in absence of catalyst, k2= A_e^{-Ea / Rx400)}

given two rates are same i.e r₁ =r ₂ k₁ =k₂





but, E<sub>a'=(Ea-20)kj/mol





Q4:-for A+B C+D,=20kj/mol.

Eaf for forwardrxn is 85 kj/mol . calculate a activation energy of reverse rxn?

Ans:- Energy of activation for farward rxn= energy of activation for backward



rxn +
Eb=85-20=65kj/mol







derive arelation in b/w k1,k2& k3



Ans:- for agiven change





2k1=k2=4k3 Q6:rate law has form , rate=k[A][B]^3/e can rxn be an elementry process?

Ans: Dumb question</sub>

Q:what is criteria for elementry process? Ans: rate law with order to molecularity (necessarily integer) are elementry process but

for given rxn.order of rxn=1+3/2=5/2 since molecularity can never be fraction so, given rxn is not elementry process

Q7:2N0+O₂2NO₂

RATE= K[NO]²[O₂] hOW will rate of rxn change if

vol. of rxn vessel is reduced to 1/4th of its original value?

Ans: Rat=k[no²][0₂

let amole of no and b mole of o2 be taken to start arxn in vessel of v at any

time. if vol of vessel is reduced to1/4 then for same mole N0 +o₂





by eq(i)and (ii)





Q8: if rate depends on conc according to eq.



,what will be the order of rxn where (a) conc. is very high (b) is very low





(a) if c is very high thn 1/c is smallest & then neglible.



= const

so, order of rxn is zero



(b) if c is very low 1+k₂c =k'





so order of rxb is unity

Q9: for 2A + B + C(excess)products.

calculate (1) rate expression

(ii) effect on rate if conc of ais doubled & of

b is tripled & c is doubled of conc of c

(i) rate= k[A],²[B]¹[c]⁰

(ii) let intial conc of a, b,c be a,b, c respectively



r 1= k(a)²(b)(c)⁰-------(1)



now,[A]=2a;[B]=3b [c]=2c

r₂=k(2a)²(3b)(2c)⁰



r₂12(a)²(b)(c)⁰



by eq (1) and (ii)