Question

Please answer these question:

_ An aqueous solution of a weak acid, HWk (pKa=5.25), has a pH of 4.53 . calculate the molarity of the weak acid.

_ A 0.15M solution of a weak base was found to have a pH =9.26 . calculate the Kb for this base.

Answer 1

Answer Let Go is molarity of weak ald ICE hable HA CON = Home Initial Change equilibrium ka = [HT] [A] MA) ka = x² Now pH - Llog H+) 4-53 = -log (47) SHI) = 10-4.53 1H1) = 2.95X 105 (H1) = * = 2.95 110-5 pka = -log ka 5.25 = -logka kq = 10-5.25 - 5.62 Xco-6

5.62 x 10-6 = (2-96 6.- (2.98x10-5) ↑ 6-(2.95X10-5) = 1.5485 710-4 = 1.84 X10 M i nitial concentration of weak acid Ile table BH+ e + 0 0.15M -X 0.13_n Kp = But] four] (B) 0.15-5 pH = 9.26 at 25°C pH + poh = 14.0 pohta 14. opH 14.0 -9.26 = 4.74 pon -log [OH-] = 4.74 OH-] = 10-4.74 = 1.82 X10-5

2. 21 X{o-9 | Ki = (A-o/Kz 8-1) - 51.0 - (-s-0IX28 -1) - = १ - 5-0) ४८४ | = = E-HQ] r-51.0 २८ = पत्र