Chemical Equilibrium Formulas

Support your learning regarding the Concept of Chemical Equilibrium with the List of Formulas prevailing. Grab the opportunity and make the most out of the Chemical Equilibrium Formulae Sheet to have a grip on the concept. Use the Formulas for Chemical Equilibrium to have a quick revision and learn the fundamentals involved.

1. Free Energy changes (ΔG):

• If ΔG = 0 then reversible reaction would be in equilibrium.
• If ΔG = (+) ve then equilibrium will be displace in backward direction.
• If ΔG = (-) ve then equilibrium will displace in forward direction.

2. Rate of Reaction (r):
(a) If A + B \(\rightleftharpoons \) C + D
r = – dC_A/dt = – dC_B/dt = dC_C/dt = dC_D/dt

(b) For 2A \(\rightleftharpoons \) C + 1/2D
r = – dC_A/2dt = dC_C/dt = 2dC_D/dt

3. (a) K (Equilibrium Constant Kc & Kp) is constant, Factors other than temperature & stoichiometry of reaction do not affects its value.

(b) For endothermic reactions: (ΔH = + x KCal)

(c) For exothermic reactions: (ΔH = – x KCal)

4. For n₁A + n₂B \(\rightleftharpoons \) m₁C + m₂D

• K_c\(\frac{[\mathrm{C}]^{\mathrm{m}_{\mathrm{l}}}[\mathrm{D}]^{\mathrm{m}_{2}}}{[\mathrm{A}]^{\mathrm{n}_{1}}[\mathrm{B}]^{\mathrm{n}_{2}}}\)
• K_p\(\frac{P_{c}^{m_{1}} P_{D}^{m_{2}}}{P_{A}^{n_{1}} P_{B}^{n_{2}}}\)
• K_p = K_c(RT)^Δn
• Partial pressure of any gas = mole fraction × total pressure

Note: This formula is used at equilibrium
(e) At equilibrium r_f = r_b

5. (a) Practical Verification of Law of Mass action → Bondenstein

(b) Equilibrium in liquid state
CH₃COOH(l) + C₂H₅OH(l) \(\rightleftharpoons \) CH₃COOC₂H₅(l) + H₂O(l). was firstly studied by Berthelot & Gilies.

6. (a) x = \(\frac{\mathrm{d}_{\mathrm{t}}-\mathrm{d}_{0}}{\mathrm{d}_{0}}=\frac{\mathrm{M}_{\mathrm{t}}-\mathrm{M}_{0}}{\mathrm{M}_{0}}\)
for PCl₅ \(\rightleftharpoons \) PCl₃ + Cl₂
Mol. wt. & Vapour density of PCl₅ are 208.5 & 104.25 respectively, vapour density = mol. wt./2

(b) In General if A \(\rightleftharpoons \) nB then x = \(\frac{d_{t}-d_{0}}{(n-1) d_{0}}\)

7. Some other important points:

• Kc unit → (moles/lit)An
• Kp unit → (atm)^Δn
• Total moles at equilibrium = [total initial moles + Δn (x)]
• Time required to establish equilibrium α 1/Kc
• If in any heterogenous equilibrium solid substance is also present then its active mass & partial pressure is assumed 1.

Le chatelier’s principal:

• Increase of reactant cone. (Shift forward)
• Decrease of reactant cone. (Shift backward)
• Increase of pressure (from more moles to less moles)
• Decrease of pressure (from less moles to more moles)

8. Summary various homogenous equilibrium:

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