Question

Design a buffer that has a pH of 9.89 using one of the weak acid/conjugate base systems shown below pК, к, Weak Acid Conjugate Base C202 НС-04 4.19 6.4x 10-5 НРО 2- Н.РОД 7.21 6.2 x 10-8 со,2- НСОЗ 4.8 x 10-11 10.32 How many grams of the potassium salt of the weak acid must be combined with how many grams of the potassium salt of its conjugate base, to produce 1.00 L of a buffer that is 1.00 M in the weak base? grams potassium salt of weak acid = grams potassium salt of conjugate base =

Answer 1

Aa) SInce due t close to PM o9. 2- Pka ofta 3 2 wuch is that g hcoCo3 dhe best buffe wil be fomed by de Companeuts han ph is Closen to Pka value, buffens knco and k2 o. This s be cause Wok begt To cal aulat e molaat of weak acid salt we Com e e hendea son- Hagul balch eguation p Pka log Ceonigate bage) C weak acid

pkat log Cco С ио] P giueu hat: pH buffe 9.89 Pka buffex o 32 Ca 2- 100M Substttating dhe ue ean.4) va lueg n 9. 89 0- 32 uco log 9.89-10 32 - O.43 Сисо] Гog1 - log Cucog) 0.43 log O 43 O 43 }O 2.61531 8 M CHo

КИlаз > Kt + Hcog K2 co 2Kt + Co2- (3) Fom ean 2) Ки соg gines Com See dhat Imole ot I mole of nco3 Thu Cn co lenco)2.15348M No q molag ofsalute nle know hat molooit Volume of Solutton ihlites J00L ginen Volume buffea Thu, gubstitu ting dhe values n ean 4) we hame Suite (kuo3) No q moleg 2.691 534 8 M L Thug No moleg Khco,2 915348mol x1 2 b115348 mo|

Kna hat No o Moleg wie given may Molas mas No Maes of knco3 Molaa mags kHlo3 Molas mags 100 5gmof Thu, substita timg dhe values ih egn 6) haue 6915348 mof we Мag a kucoз Mags of kco- 2.b915318m6 X too-53 269.463007 9 Siueu dhat Molasita o weak bage = 10OM Thatis, co-] = 00M l mole he Com See hat From ean 3), а Кр соз grиeз I mole g Cog2-. oOM Thus, Ceo2Ck, co2] Molasity kco3 x Solitfon ih litens No o mdeg k2 co3= Yolume oOM x 00L 0omx

Mags K23 f) moleg c K2 C03 N Also Molas mag Molas mags o K2c03 13 8. 2059/mof egn We houe Substrtn ting dhe valueg Mass of KCo3 38.205 moj No of moles o K2c3 - Mags to3 oomol 138.2053/mof xl-00 Mass a Kco 13 8.205a 138-205 1389 nams Potassiam salt of Weak ac Mass o Kn Mass in 2690 Mass ng4ams o potbassiu Salt o Conjugate base 1389 Mars K2CO3