Question

When a weak acid solution is diluted by half, the fraction of ionized weak acid increases. Using the reaction quotient, demonstrate this effect and explain why the increase in ionization occurs.

Answer 1

Also why is increse in ionization occurs on dilution is because of the fact ,On dilution of weak acids it dissociates into ions because of high dielectric constant of water. on dilution ions are readily available and consequently the degree of ionisation increases

21 Let us take a weak aud , macetic aud, The lonisation of autic aid taky place os! cң соон д cңCO0" + H* initial 10m 0 0 at equilibrium (1.0-1) where, 1.0M = concentration of autic and initally present, na change in concentration at equilibrium. Ka = [CH3600"] [Ht), ** * - 175x105 (giver) TCH₃600H) (1.0-1) (1.0-x)" [CH₂COOH] = 1.0 - 570007 400, so n << 1.0. na 1.75810-5 - Stoooy 400, so Ra then 12 = 1.758105 112=1.75 X 105 1 75 X 105 [H] = x moll L=4.18 X 103 mol/ L will n = 4.108 10-3 34 y lonisation [H+) x 100% = 4.10X10 ImollLXlvoy = 0.42% (CH, 0 0 0 1.0 mol/L Now, when diluted and is made, consider, concentration has been halved (0.50 mol/L to initial concentration, then, at equill brium, change in concentration of aud = 0.50-1, then reaction quotient, K= [HJ LanLool Nox 1.758105 [Choou ] 0.50.1" 99000 y 400, so, 20.50 Ka 1.75 XION ther 240.50. Or 72 = 1.75X10-5, & 12 = 0.500 1.75 X 105 = 8.75 X 106, 1 = 10.758 10-6 = 2.96 X 103 y lonis attons 2.96 X 10-3 molll yox 0.59% 0.50 moll . The tonisation increses as the concocentration decreses. 0:50 0.50 arvot