Equilibrium Formula List in Chemistry

1. Law of Chemical Equilibrium
    aA + aB + ....      ⇌     xX + yY + ....

• [X]^x[Y]^y
  ---------- =    K or K_c
  [A]^a[B]^b

2. Relationship Between K_p and K_c

• K_p   =   K_c(RT)^△n

3. Law of Chemical equlibrium in terms of a Activities
Strictly Speaking, Activities are used in place of molar concentrations

• Activity = Activity coefficient × Molality (or Molarity),i.e.,
  a = γ × m
  For the reaction,    aA + bB ⇌ xX + dD,
  or        a^c_C × a^d_D
      K_a = ------------
              a^a_A × a^b_B

4. Equilibrium constant in terms of mole fractions(K_x).

• Consider the general gaseous reaction:
  aA + bB ⇌ cC + dD
  If at equlibrium, the mole fractions of A,B,C and D are x_A, x_B, x_C and x_D resepectively then
             x^c_C × x^d_D
    K_x = ------------
              x^a_A × x^b_B
  Similar to the relation between K_p = K_c, we have,
  K_p and K_c(RT)^△n

5. From the relation, K_p = K_c(RT)^△n,
we may conclude that

• If △n = 0, K_p = K_c
• If △n = +ve, (i.e. n_p > n _r),K_p > K_c
• If △n = -ve, (i.e. n_p < n _r),K_p < K_c

6. Henry's Law

• 
  m ∝ p or m = kp
  where k is a constant of proportionality and is called "Henry's constant".
  It's value depends upon
  - Nature of the gas,
  - Nature of the Liquid and
  - Temperature.