Question

Part 1.)

Consider the titration of 50.0 mL of 0.0500 M C₂H₅NH₂ (a weak base; K_b = 0.000640) with 0.100 M HBrO₄. Calculate the pH after the following volumes of titrant have been added:

(a) 0.0 mL pH =	(b) 6.3 mL pH =	(c) 12.5 mL pH =
(d) 18.8 mL pH =	(e) 25.0 mL pH =	(f) 42.5 mL pH =

Part 2.)

A solution of Na₃PO₄ is added dropwise to a solution that is 0.0613 M in Ag⁺ and 0.00490 M in Cu²⁺.

The K_sp of Ag₃PO₄ is 8.89e-17.
The K_sp of Cu₃(PO₄)₂ is 1.4e-37.

(a) What concentration of PO₄^3- is necessary to begin precipitation? (Neglect volume changes.)
___ [PO₄^3-] =  M.

(b) Which cation precipitates first?

___ Ag⁺Cu²⁺    

(c) What is the concentration of PO₄^3- when the second cation begins to precipitate?
___ [PO₄^3-] =  M.

Answer 1

(0-1 ) Pétrant is > HBrO HBX Oy (a) VreBron = ome to Iperbromic land) C#, NH, + H 9 o.osm 50ml, 0.05m ." "" = C, H , 1 of. I Ab tzo ķ= 6oYX10" 0:05-n 7 tot 0,05M [CH, NM, ] [ 08] .=Kb = 6:4 8109 [C, 45NH2] [ho] bactrity of pure liquid is considered to be unity *8634x1024 = x= 0.32x1074 32732x10-6 [on] 2 ** 5,65 X 17M polt -log Condo - logbias x103) = 2,248 (pH = 14-poh = 11.7527 (6) Hora 6.3me klimating reactanding seases [ from HBron ... ICH NA tur) мер рә orxъ M ) s - C₂ H₂ N H + H₂o keeksha 42 (Ks), IN 563 22.5 6.3x oul 56) K 1s Neutralisation 0263 764X10-9 5613 1,87 Mydrolysis by loty 0.63 7.3 2634X10

6:4X10o = 0.63 TRT [MT] = no 0.63 x10-10 1,87 Xboy (Helo 0.053x10 to pHe slog. Cht) = -loglo.os3x1540) = fhay, 0, 01'3 + hoy no-ro] logovor? +10 - 1.275. 1.2 12 5me s from HBr Oy Linkting reagen [CM, NH, Dal) - +18) - (LI, NN, (aq) + ho, Kega 604x160 - 5080005 - 62,5 25 T25 12,5X 0-1 62.5 1,25 fate nes te 1,25 + 1.25 125- 62.5 21.25 * 1:25 62.5 Keq 2 614 X100 = 1 12 XXX HET CK"]. *: x": 0,15% xlo ve (pH a heg (14) = 10081

(d) Vuoro. 1818ml winding noudandi GH, NH, (ag) +Ho) - Gas Cap) e 1o, Kaga 6,4 2150 - о, оr xo tet 12.31 62.8 6818 - 2.5 68.8 1. PP 63, 0-62 6818 6.8.8 1.88 0.62 - th 68.8 68.8 CP.8 Ke 26.48lolo lose Pr8x* *0.62 [Mt) - no 0.474 Xulo - [pho-log Chr] = 10.324) res VHbrou a 25me, CHANH, (a) tho 2 CH_NH (aq) + Ho, Kega 674X1000 /% 50 3อา 25-Xo | - 75 a 2,5 .but 2.5 x Reg. 6.4 xide 2.5 7542 22,5.01x1,-1] Сн") » = 0,га, хоги CHT) = 0.722x10-6 pH = -log [HT] . 6.14. Ab tatay 2. 2 2.5

12 IF 1 - C₂H, N4 ho, kep= 6.4815". Ab VARU 2 42.5ml C₂ M₂ NH₂ (2) TH® soxo.os 0x42.5 92.5 92.5 22.5 9205 a 4,25 92.5 1.75 2,5 92.5 92.5 At 92.5 n tatay . 92.8 ł 1.75 92.5 92.5 - The tipo lieta 0.0189 . =) phe-boy, I'M *). -logo.018) 92.5 21.7 21 Part 12) Ag Poy (1) - 3 Agt (aq) + poy Taal (Ksp) = 8,8981017 given Ksp = 8.89x1017 - (Aghy poy332 21 - (as [ty Poy (1)} = unity - activity of pure solid 60.0613] [p0, 1] = 88981.317. Crown] 3.86 x 103 m unsty) "ancentration of pour required to precipitate Ago, ů censidered to be

- 1.4710-17 Cuz Pow). (1) 2 3 " (as) + 2104 (ap), Ksp = 1.4x1537 [ur} [punya 12 | Cutto4), 4) ] • Laity ) (0.00493°C por 2 = 114x10-17 Cro??? Hey 1019 x 10-20 I CIPOG?] 1.091815-15M 7 sancentration of our required to precipitate out cu 24 * (a) Pou must a concentration equal to (1.011 X 155 M) so as to be precipitation, (b) u²t will precipitate forsts as les concentration - required to precipitate this cuit cation . of po?-ü ice second cation (Ag) will begin to precipitate once [post] becames equal to 3.86 X/51M.