Equilibrium
a state where opposing forces are equal. It can only be achieved in a closed system. All the external properties are constant
Different types of equilibrium
1.Static: after reaching equilibrium point there in no motion in the system
2.Dynamic: after reaching equilibrium point, there is motion in the system but no net movement
a. Physical equilibrium: state transformation of dissolution
b. Chemical equilibrium: in chemical reaction
c. Ionic equilibrium: in ioin reactions
How is Kc and Qc different?
Qc is a constant at any given concentration and temperature. While Kc i s equilibrium constant measured at equilibrium point
Law of mass action
rate of reaction is proportional to the molar concentration
forward reaction = Kf[A]^a[B]^b
backward reaction = Kb[D]^d[C]^c
chemical equilibrium law
The ratio of concentrations of the product to the reactants raised to the power of coefficients in equilibrium at a given temperature .
at equilibrium
rate of backward reaction = rate of forward reaction
kc=Kf/Kb =[D]^d[C]^c/[A]^a[B]^b
Equilibrium constant
there are two types:
1. Concentration (Kc)
2. Partial pressure (Kp)
Kp= kc(RT)^Δn
Δn = no. of moles of product - no. of moles of reactant
Features of equilibrium constant
- Can help in predicting the extent of reaction
X>10^3 - complete reaction
10^3 - 10^-3 - same amount of reactant and product
x<10^-3 - the reaction rarely happened
Factors affecting chemical equilibrium
- Temperature
a) if temp of the system is increased then the for equilibrium it must be reduced
b) if the temp is reduced that foe equilibrium it must be increases - Pressure and Volume
if pressure increases , volume decreases and concentration increases
a) pressure increases shift towards less no. of moles
b) volume increases shift towards the more no. of moles - Concentration
a) if added the reaction uses it
b) if removed the reaction produces it
Physical equilibrium
- State transformation
a) S<->L
b) S <-> G
c) L<->G - Dissolution
- Solid in liquid (saturation point )
- Gas in liquid (pressure)
Henry’s law
the mass of gas dissolved the solvent as at given temperature is proportional to the pressure above the solvent
Relation between gibbs free energy and equilibrium constant
ΔG = -RT ln(k)
k = e^ -ΔG/RT
k>1 G>0 spontaneous
k<1 G<0 not spontaneous
Define the equilibrium constant for
1. reversed reaction
2. when two reactions are added
3. when two reactions are substrate
4. when a number is multiplied with the reaction
- k’ = 1/k
- k’ =k1.k2
- k’ = k1/k2
- k’ = (k)^n
The unit of equilibrium constant
- concentration
unit = (mol/l)^Δn - pressure
unit = (bar)^Δn
As per Faraday how were substances classified?
- Electrolytes : conduct electricity
a) weak : partial dissociation
b) Strong: complete dissociation - Non electrolytes: doesn’t conduct electricity
Define
1. Ionization
2. Dissociation
- the no. of ions formed
- the no.of ions formed in water
in this context are interchangable
Define acid and bases
- Acids
a) give/ donate H+ ion
b) accept lone pair
c) ka = cα^2/1-α
d) pka = - log(ka) - bases
a) take H+ ion
b) give OH - ion
c) accept lone pair
d) kb = cα^2/1-α
e) pkb = - log(kb)
Ionization constant of water
Kw = [h3O+][OH -]
[h3O+] = [OH -] = 1* 10^-7
kw = 1*20^-14
pH
negative log
pH = -log(H+)
pOH = - log(oH-)
pka + pkb = 14
pH> 7 = base
pH< 7 = acid
pH = 7 = salt
Common ion effect
when a substance contain the same ion is added then it causes a shift in equilibrium
Buffer solution
A solution that resists the change in pH by adding a acid or base in it
Conjugate pair
A pair of acid and base that differ by one H+ ion
Solubility
the degree to which the substance is soluble
Ksp = (S.X)^x (S.Y)^y
Factor affecting acidity
The factors affecting acidity:
1.Bond strength increases acidity decreases
2. Polarizing ability increases acidity increases
Factors affecting solubility
- lattice enthalpy
- Solubility enthalpy
S.E>L.E then more soluble
