Question

Maleic acid contains two carboxylic acid groups, one with a pka of 2.0 and a second with a pKa of 4.0. The fully protonated from of malice acid is shown on below. Briefly describe how you would prepare 0.25L of a 0.1 M buffer at pH = 2.0, assuming that you are starting with the disodium salt of the acid. You should give the moles of sodium malate (MW 178.05 g/mol ) and HCL (36.46 g/mol) that you would need to make this buffer.

Understand: Maleic acid contains two carboxylic acid groups, one with a pKa of2.0 and a second with a pKa of 4.0. The fully protonated form of maleic acid is shown on below. Briefly describe how you would prepare 0.25L of a 0.1 M buffer at pH=2.0, assuming that you are starting with the disodium salt of the acid. You should give the moles of sodium malate (MW 178.05 g/mol) and HCl (36.46 g/mol) that you would need to make this buffer. HOO

Answer 1

Maleic aeid fran folly frstonated fm diosociates as: Pka pkar (A2-) HA is cegate bane (Ca) of MaA (aeid) Simalanly A2- CE afH (aeid) afen 4 buffeha bffeing paeily PHYamgeis pKa-topka fthe buff ering apaeiy io anaxianu en PHPRa Jo, here pka, aeak aeid HAin cen ati kane ofHa New, from Henderren tanehaleh eauatin we get PH PKat 2.n to be cenaidergd ah ahene [A) A Jeid Bog Ceny CA Rere /0 4CB: AA CA CCRCAG Buffer comcentralienh o Sor aing t nan balanee eauahon E A) Ce: 0.25 Cea). C) CAJ CA 0.25 2 LA) 0.25 . CA) 015h 0.125

.For 025L ofbufferr anoles of Aip. H 4 auill be mudad O.125mal -2 3/ASX0anol amolen of Ce A HAai k needed aho anel formed froun WMHAHHA au disodium sat of tha aeidd i NarA Na (u 7o tal ameln of HA HA ase 3/as3-12s X10 mo/ - 6.250X6 me Moler of dis odum aalt aull ée needed 6.2,50 XIO m/ Wew dinodiumm an/t (Nar aull rgaet Certtu Hel an NaH A c -fi) Na HA Hcl HA +Nacl AcC 6-250 X16-4mol Na A reat aut 6150x16 u Ha convavt pd t 6.250x/0anel NaHA pain,ain ce i the fimal dufer Astution & frpaons. Sh aceording 4 Yeartioni) 3'/25x /6amo HA uill e formed y 3.1aM5X16msl NaHAL ?'/aSx/0 no/ tel NAHA n (6.50- 3./as x/6anul Acenaining = 3'/25 X/6 will de vearuved Total H c (6-&50 9.12.s)x/4 anol 9.375 X/0 mo

dinodivm na/t f analate Molas man of dirodium nalt malal /7858 11-1 4mam af HLl meeded 9.375xmsl 36.46 amer