chemical equilibrium notes

Chemical equilibrium
The state at which the concentration of reactants and products do not change with time is known as a state of chemical equilibrium.

Reversible and Irreversible rection
Those reaction which complete in only in one direction is known as Irreversible reaction
Those reaction which take place in both forward and backward direction is known as Reversible reaction.

Equilibrium
The condition at which some of the measurable property like Pressure, Temperature, etc become constant is called Equilibrium.

About Equilibrium

1. Equilibrium is dynamic in nature.
   
2. At Equilibrium, the rate of both forward and backward is same.
   
3. The state of equilibrium can be achieved from both forward and backward side.
   
4. The state of equilibrium can only achieved in case of Reversible reaction.
   
5. At state of Equilibrium, it is not necessary that the concentration of reactant and product is same. It may or may not be same.
   
   

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   Physical and Chemical Equilibrium
   The reversible process in which the components of reactant and product do not change, only change in phase will take place at Equilibrium is called Physical Equilibrium.
   Example:-> H₂O_(solid) <---> H₂O_(liquid)

   The Reversible process in which the Chemical components of reactant and product are different with respective phase change is called Chemical Equilibrium.
   Example :-> N_{2 (gas)} + 3H_{2 (gas)} <---> 2NH_{3 (gas)}

   Homogeneous and Heterogeneous Equilibrium
   If all reactants and product are in same phase, then the Equilibrium attend is called Homogeneous Equilibrium.
   Example :-> 1. N_{2 (gas)} + 3H_{2 (gas)} <---> 2NH_{3 (gas)}
   2. CH₃COOCH_{3 (liquid)} + H₂O _(liquid) <---> CH₃COOH_(liquid) + CH₃OH_(liquid)
   If atleast one of reactant or product are in different phase, then the Equilibrium attend is called Heterogeneous Equilibrium.
   Example :-> 1. CaCO_{3 (solid)} <----> CaO_(solid) + CO_{2 (gas)}
   2. 2Na₂O_{2 (solid)} + 2H₂O_(liquid) <-----> 4NaOH_(liquid) + O_{2 (gas)}

   NOTE :-> All the decomposition reaction are endothermic in nature which means heat is always supply for breaking bonds.

   Law of Mass action
   According to this rule, "The rate of any chemical reaction is directly proportional to its active mass to the power its stiochiometric coefficient."
   

   aA_(gas) + bB_(gas) <------> cC_(gas) + dD_(gas)
   (rate)_(forward) proportional to [active mass of A]^a[active mass of B]^b
   The active mass of pure solid and liquid is taken as unit.
   (rate)_(forward) = K_f [active mass of A]^a[active mass of B]^b
   [ where K_f is proportionality constant for forward.]
   (rate)_(forward) = K_f [aA]^a [aB]^b --------(1)
   (rate)_(backward) = K_b [aC]^c [aD]^d -------(2)
   [ where K_b is proportionality constant for backward.]
   from (1) and (2)
   K_f/K_b = [aC]^c [aD]^d/[aA]^a [aB]^b
   K_f/K_b = K_Equilibrium
   K_Equilibrium = [aC]^c [aD]^d / [aA]^a [aB]^b
   [K_c = Equilibrium constant in term of concentration.]
   K_c = [C]^c [D]^d / [A]^a [B]^b
   Active mass-pressure
   K_p = [Pc]^c [Pd]^d / [Pa]^a [Pb]^b
   Active Mole fraction
   K_X = [Xc]^c [Xd]^d / [Xa]^a [Xb]^b
   

   PV = nRT -------- (ideal gas equation)
   P = nRT / V
   P_A = [A]RT
   P_B = [B]RT
   P_C = [C]RT
   P_D = [D]RT
   

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   K_Equilibrium = [[C]RT]^c [[D]RT]^d / [[A]RT]^a [[B]RT]^b
   K_Equilibrium = {[C]^c [D]^d / [A]^a [B]^b} * (RT)^(c+d)-(a+b)
   This formula is only for those which are in gas phase.

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For Endothermic reaction, K increases with increase in temperature.