Chemical Kinetics Flashcards
What is rate
Decrease in conc of reactant in unit time
OR
Increase in conc of product in unit time
Rate of the reaction:
A –> B
in terms of A
-∆[A]/∆t
Rate of the reaction in terms of B
A–> B
∆[B]/∆t
What is the unit of rate
conc/time
Avg rate and instantaneous rate of the reaction:
A–>B
Avg rate: -∆[A]/∆t OR ∆[B]/∆t
Instantaneous rate: -dA/dt OR dB/dt
What is law of mass action
It states that rate of reaction is directly proportional to conc of reactants
R=K[A]
R=K[A]
what is ‘K’ in the rate eqn?
‘K’ is a constant known as rate constant OR specific reaction rate
On what factors does rate constant, K depend on?
Temp.
The rate constant for a reaction at a particular temp is constant
What is order?
Order is the sum of powers of conc terms in a rate eqn
Integrated rate eqn of first order reaction
2.303 log [Aₒ]/[A] = Kt
Integrated rate eqn for zero order reaction
[Aₒ] - [A] = Kt
Half life for first order reaction
0.693/K
Half life for zero order reaction
[Aₒ] / 2K
Order of radioactive decay
First order
Arrhenius equation
K = Ae ^ (-Eₐ/RT)
K: rate constant
A: arrhenius constant
Eₐ: activation energy
R: universal gas const
T: temp in kelvin
Logarithmic form of arrhenius equation
logK = logA - Eₐ/2.303RT
Enthalpy change of endothermic reaction ∆H
∆H = Eₐ (forward) - Eₐ (backward)
In NH₃ synthesis by Haber’s process, what is the effect on the rate of the reaction with the addition of Mo and CO, respectively?
- When Mo is used as catalyst, it increase the rate of formation of NH₃ because it behaves as promoter
- when CO is used as catalyst it decreases the formation of NH₃ because it behaves as poisoning agent.
Effect of catalyst
- increases the rate of the reaction
- provides an alternative path of lower activation energy
- doesn’t change enthalpy of reaction
- enhances both forward and backward reaction at the same rate
