Online Formulas on Chemical Kinetics ( Chapter=> 4)

These are Online Formulas on "Chemical Kinetics" ( Chapter=> 4) for
practice of CBSE BOARD, CBSE NEET, CSIR NET Chemical Science etc.

Formulas List on "Chemical Kinetics":
1. Instantaneous rate = dx / dt     
where dx is small change in conc. and dt is the smallest interval of time.

2. Average rate = Δx / Δt

where Δx is change in concentration and Δt is large interval of time.

3. A + B → C + D

Rate of disappearance of A = - d[A] / dt
where d[A] is small change in conc. of ‘A’ and dt is small interval of time

Rate of disappearance of B = - d[B]/ dt

Rate of appearance of C = + d[C] / dt
Rate of appearance of D = + d[D] / dt

Rate = - d[A] / dt =  - d[B] / dt = + d[C] / dt = + d[D] /dt

Unit of rate of reaction = mol L^-1s^-1

4. Order of reaction:
If rate law expression for a reaction is

Rate = k [A]^x [B]^y

Order of reaction = x + y

Remember: Order cannot be determined with a given balanced chemical equation. It can be experimentally determined.

5. Integrated rate law for zero order reaction:
R → P
dx / dt = k[R]⁰

Unit of ‘k’ is mol L^-1s^-1

k = {[R₀] - [R] }/ t

If we plot a graph between concentration of R vs time, the graph is a straight line with slope equal to -k and intercept is equal to [R₀].

6. Half- life reaction for a for zero order reaction:
t_1/2 = [R ] / 2k

7. Rate law for 1^st order reaction:
R  ==> P
k  = (2.303 / t) (log [R₀] / [R])

where ‘k’ is rate constant or specific reaction rate, [R₀] is initial molar
conc., [R] is final molar conc. after time‘t’.

If we plot a graph between ln[R] with time, we get a straight line whose
slope = - k
and intercept ln[R₀]
k  = (2.303 / t) (log [a] / [a - x])
where ‘a’ is initial conc. in mol L-1, x mol L-1 have reacted in time ‘t’
final conc., after time ‘t’ is (a – x).

8. Half- Life for a first order reaction is:
t_1/2 = 0.693 / k

9. Formula to calculate rate constant for first order gas phase reaction
of the type
A(g)  ==>  B(g) + C(g)
k  = (2.303 / t) (log [P_i] / [P_i - P_t])
Where:
P_i is initial pressure of A
P_t is total pressure of gaseous mixture containing A , B, C
Remember:
p_t = p_A + p_B + p_C

10. Arrhenius equation:
k =Ae ^-E_a ^/RT

11. log ( k₂ / k₁) = ( E_{a /} 2.303 RT )  [ (T₂ -T₁ ) / T₁T₂ ]

12. Rate = P Z_AB . e ^-E_a ^/RT
Where: Z_AB represents the collision frequency of reactants, A and B
e ^-E_a ^/RT represents the fraction of molecules with energies equal to or greater than ^E_a 
P is called the probability or steric factor.