Equilibrium can be established for both physical and chemical processes and at equilibrium rate of forward and reverse processes are equal. Equilibrium constant (K_c) is expressed as the concentration of products divided by reactants, each raised to Stoichiometric Coefficient. K_c has fixed value of constant temperature and at this stage concentration, pressure, etc. become constant. K_p is equilibrium constant in terms of partial pressure of gases or vapours. The direction of reaction can be predicted by reaction quotient Q_c and Q_p Q_c = K_c at equilibrium and Q_p = K_p Le Chatelier's principle states 'Equilibrium' will shift in the direction so as to counter balance the effect of change in T, P and conc. The equilibrium between ions and unionised molecules in weak electrolyte is called ionic equilibrium.
(a) At a certain temperature Kc = \(\frac{9}{4}\) for the reaction:
CO(g) + H₂O(g) \(\rightleftharpoons\) CO₂ (g) + H₂ (g)
If we take 10 moles of each of four gases in one litre container, what will be concentration of H2 at equilibrium?
(b) In the equilibrium CO(g) + H₂O(g) \(\rightleftharpoons\) CO₂ (g) + H₂ (g) if at a given temperature, the concentration of the reactants are increased, what will be the value of equilibrium constant K_c.
(c) If the value of an equilibrium constant for a particular reaction is 1.6 x 10¹², what will be present in the system at equilibrium.
(d) The K_sp of AgCl, AgBr, AgI are 1.8 x 10^-10 , 5.0 x 10^-13 , 8.3 x 10^-17 , which will precipitate last if AgNO₃ solution is added to NaCI, NaBr. NaI?
(e) The equilibrium constant for reaction N₂ (g) + 3H₂ (g) \(\stackrel{K_{1}}{\rightleftharpoons}\) 2NH₃(g) is 49, what is equilibrium constantfor NH₃(g) \(\stackrel{\mathbf{K}_{2}}{\rightleftharpoons} \frac{1}{2} \) N₂(g) + \(\frac{3}{2}\) H₂(g)?

Observe the table of the ionisation constants of some common polyprotic acid at 298 K. Answer the questions based on this table and related studied concepts.
The Ionisatlon Constants of Some Common Polyprotic Acids (298K)

(a) Why is K_a1 greater than K_a2?
(b) Arrange K_a1, K_a2 and K_a3 in phosphoric acid.
(c) Why is K_a1 >>> K_a2 in sulphuric acid?
(d) What is relationship between K_a1, K,_a2 and K_a3?
(e) Write expression for K_a1 and K_a2 and K_a of H₂CO₃
(f) What is basicity of H₃ PO₄?
(g) Out of oxalic acid and citric acid, which is stronger?

Arrhenius acids give W ion in aqueous solution where as bases give OIr in aqueous solution. Bronsted acids are proton donor where as Bronsted bases are proton acceptors. Acids, on donating proton form conjugate base where as bases form conjugate acid after accepting proton. Buffer solution is a solution whose pH does not change by adding small amount of H⁺ or OH^-. The decrease in conc. of one of the ion by adding other ions as common ion is called common ion effect. Lewis acids are electron deficient or +vely charged. Lewis bases are electron rich or negatively charged, K^sp (solubility product) is the product of molar concentration of ions raised to power number of ions per formula of the compound in sparingly soluble salt. Precipitation occurs only if ionic product exceeds solubility product. Solubility of salt decreases in presence of common ion. K_W, is ionic product of water, 1 x 10^-14 at 298 K. K^W, increases with increase in temperature. pH is -log [H₃O₊] where [H³O⁺] = C\(\alpha\) in monoprotic acid 'C' is molar cone.,'\(\alpha\)' is degree of ionisation. A salt is said to be hydrolysed if pH of solution changes. K_H is hydrolytic constant. pH of salts of strong acid and strong base is equal to 7. pH of other salts can be 7. pH of buffer solution can be calculated with the help of Henderson equation.
pH = pKa + \(\log \frac{[\text { Salt }]}{[\text { Acid }]}\) 
(a) What win be conjugate base of
(i) H₂ SO₄
(ii) H\(\mathbf{C}{O}_{3}^{-}\)\(\)?
(b) What are conjugate acids of 
(i) \(\mathbf{N H}_{2}^{-}\) 
(ii) NH₃
(c) The conc. of [H₃O⁺] is 4 x 10^-4. What is pH of solution? [log 4 = 0.6021], log 10 = 1.
(d) K_b for NH₃ is 1.80 x 10^-5 .What will be Ka? [K_W = 1 x 10^-14]
(e) K_sp of BaSO₄ is 1.0 x 10^-10. What is its solubility?
(f) ) Calculate pH of buffer solution containing 0.01 M CH₃COOH and 0.1 M CH3COONa,pKa = 4.75.
(g) ThepK_a of CH₃COOH and pK_b of NH₄ OH are 4.76 and 4.75 respectively. Calculate pH of CH₃COONH₄ solution. (PK_w = 14)