Acid Base Equilibria

Question 1

What is Arrhenius theory of acids and bases

Answer 1

• Arrhenius acid is a substance that releases H⁺ ions when dissolved in water
• Arrhenius base is a substance that releases OH^- ions when dissolved in water

Question 2

What is Bronsted-Lowry theory of acids and bases

Answer 2

• Bronsted acid is a proton(H⁺) donor
• Bronsted base is a proton(H⁺) acceptor

Question 3

What is conjugate acid and conjugate base

Answer 3

• When a Bronsted-Lowry acid, HA loses a proton, A^- is called the conjugate base of HA
• When a Bronsted-Lowry base, B accepts a proton, the resulting product, BH^{+ is called the conjugate acid of B}

Question 4

What is Lewis theory of acids and bases

Answer 4

• Lewis acid is an electron pair acceptor
• Lewis base is an electron pair donor
• acid-base reaction: donation of an electron pair by a Lewis base to Lewis acid to form a convalent bond

Question 5

pH and pOH

Answer 5

pH = -log₁₀[H⁺]
pOH = -log₁₀[OH^-]

Question 6

Effect of temperature on K_w

Answer 6

• dissociation of H₂O is endothermic
• when temperature increases, the forward endothermic reaction is favoured and position of equilibrium shift to right to absorb the excess heat
• both [H₃O⁺] and [OH^-] increase by same extent and K_w increases

Question 7

Definitions of strong acid, weak acid, strong base, weak base

Answer 7

• strong acid is one which dissociated fully in aqueous solution to give protons
• weak acid is one which dissociates partially in aqueous solution to give protons
• strong base is one which dissociates fully in aqueous solution to give hydroxide ions
• weak base is one which dissociates partially in aqueous solution to give hydroxide ions

Question 8

pK_a and pK_b

Answer 8

• pK_a = -log₁₀K_a
• pK_b = - log₁₀K_b
• the larger the value of K_a, the smaller the value of pK_a

Question 9

What is salt hydrolysis

Answer 9

• salts dissociate into ions which then react with water to produce either acidic or alkaline solutions

Question 10

What is hydration

Answer 10

• when salts dissolve in water, the ions are attracted to surrounding water molecules through ion-dipole interactions

Question 11

What is a buffer solution

Answer 11

• buffer solution is one where pH remains almost constant when small amounts of acid or alkali is added to it

Question 12

Acidic buffer

Answer 12

• weak acid and its salt
• conjugate acid-base pair

Question 13

Alkaline buffer

Answer 13

• weak base and its salt