Question

Below is the titration curve of a weak base. Determine the following

10 pts Below is the titration curve of a weak base. Determine the following: of HC 1. The 2 endpoint volumes of HCI 2. The apparent molecular weight of the base if 0.25 g were added to the solution and the HCI concentration is 0.1 M 3. The pKb1 for the base 4. The pKb2 for the base

Answer 1

Comment in case of any doubt.

② In titration of weak base with strong acid, shoup duop in pH occurs near equivalence point. The equivalence point pt is taken to be at middle of the sharp drop and volume corresponding to the equivalence point pH (mid of sharp pH derop) to be equivalence point volume. such sharp pH declines in the given plot are observed once at Vice = 20mL and again at 40ml. So, the two end point volumes of Hel are (20ml, 40mL Moles of He used for first equivalence point 1 = Oid Mx(Qoxsözl) = 0.0020 mal so, molar mass y Rome in literes of weak base = moles of He used between - first and second equivalence number of = moles of hase moles of weak base. 0.25g = 1125g 30 At halfway to first equivalence point : [B]=[BH] KI Blaq) + HOM BHT (aq) + 04-199), Kb Base once protonated Kb. = 58M+ICOH) = [OH-] as CB3=CBH] at above point. base 10] » -logKb = -log(OH-] = poh= 14-pH uthu' mpon from slot pkb, same holdes for pking= plu-pH at find pet at lomi and (20+10= 30mL. ' at midway between - Istand and equivalen phat 10 ml a 10 and pH at 30ml ~ 6.5. You ne points : can find exact using a seale on your plot. So, we get 'pkb, ñ 14-1024 and pk bz ~ 40-6.5 27.5. ma points 0.0020 mol