Question

please show work

Use the data in the tables below. Show appropriate work for numerical calculations. K. values: HCI HNO3 H2SO4 HSO4"- H3PO4 HF HNO2 HCOOH strong strong strong 1.3 x 10-2 7.5 x 10 7.1 x 10+ 4.5 x 10-4 1.7 x 10+ CH3COOH CsH NH H2CO3 H2PO4 NH4+ 1.8 x 105 5.9 x 10-6 4.2 x 10-7 6.2 x 10-8 5.6 x 10-10 4.9 x 10-10 4.8 x 10-11 4.8 x 10-13 HCO3 HPO42- Ksp values: 8 CaCO3 CaF2 Ca(OH)2 Ca3(PO4)2 Fe(OH)2 Fe(OH)3 MgCO3 8.7 x 10-9 4.0 x 10-11 8.0 x 10-6 1.2 x 10-26 1.6 x 10-14 1.1 x 10-36 4.0 x 10-3 Mg(OH)2 AgBr Ag2CO3 AgCl Ag2SO4 Zn(OH)2 1.2 x 10-11 7.7 x 10-13 .1 x 10-12 1.6 x 10-10 1.4 x 105 1.8 x 10-14 2) (24 points) Propose buffer component to buffer a pH = 8.1. Let the base have a concentration of 0.23 M. Identity Concentration Acid Base 0.23 M

Answer 1

as a rule of thumb if you want pH around 8.1 then select that acid whose pka lies such that pH = pka -1 to pKa +1

hence pKa should be between 7.1 - 9.1 hence NH4+ would be the ideal choice so it act as acid and base will be NH3

applying Henderson equation

pH = pKa + log [base] / [acid]

pKa = -log Ka = -log (5.6*10^-10) = 9.25

and [base] = 0.23

8.1 = 9.25 + log [NH] [NH] 8.1 - 9.25 = log [NH3] [NH] -1.15 = log [NH] | [NH, Applying logarithm rule we have: 10-1.15 - [NH [NH] 0.07 = (NH3) [NH, It implies that: | 0.07 [NH,] = [NH] = 0.23 M [NH, *1 = 0.23/0.07 = 3.24 M