Summary

Summary

• According to Arrhenius, an acid is a substance that dissociates to give hydrogen ions in water.

• According to Lowry and Bronsted concept, an acid is defined as a substance that has a tendency to donate a proton to another substance and base is a substance that has a tendency to accept a proton from other substance.

• According to Gilbert . N. Lewis , an acid is a species that accepts an electron pair while base is a species that donates an electron pair.

• ionic product (ionic product constant) of water (K_w)=[H₃O⁺][OH^–]

• pH of a solution is defined as the negative logarithm of base 10 of the molar concentration of the hydronium ions present in the solution.

pH = –log ₁₀ [H₃O⁺]

• when dilution increases, the degree of dissociation of weak electrolyte also increases. This statement is known as Ostwald’s dilution Law.

• When a salt of a weak acid is added to the acid itself, the dissociation of the weak acid is suppressed further this is known as common ion effect

• Buffer is a solution which consists of a mixture of a weak acid and its conjugate base (or) a weak base and its conjugate acid.

• Buffer capacity and buffer index is defined as the number of gram equivalents of acid or base added to 1 litre of the buffer solution to change its pH by unity.

 Î² = dB/d(pH)

• Henderson – Hasselbalch equation For Acid buffer

⇒ pH = pK_a + log ([acid]/[salt])

For Basic buffer

⇒ pOH = pK_b + log ([base]/[salt])

• Hydrolysis of Salt of strong base and weak acid

K_h .K_a =K_w

pH = 7 + ^1/₂ pK_a + ^1/₂ log C.

• Hydrolysis of salt of strong acid and weak base

 K_h .K_b = K_w

pH = 7 – ^1/₂ pK_b – ^1/₂ log C.

• Hydrolysis of Salt of weak acid and weak base

K_a .K_b .K_h =K_w

pH = 7 + ^1/₂ pK_a – ^1/₂ pK_{b .}

• The solubility product of a compound is defined as the product of the molar concentration of the constituent ions, each raised to the power of its stoichiometric co – efficient in a balanced equilibrium equation.