Question

3. Alkalinity is related to the buffering capacity of an aqueous solution containing an acid and its conjugate base which can be understood using the Henderson-Hasselbalch equation, as follows. pH pKa log [base/[acid] where Ka is the acid dissociation constant. Calculate the pH of a buffer solution that is 0.050 M in benzoic acid (C6HsCOOH) and 0.150 M in sodium benzoate (CsHsCOONa). Note: Ka (benzoic acid) 6.5 x10. Outline any assumptions or simplifications in your calculation. What will happen to the final pH of the benzoic acid/benzoate solution if Fe2+ (aq) is added and complex formation occurs according to reaction [3]? The value of the formation constant is as follows: Kf (Fe(CeHsCO0)2)- 1.5x1010 K, Fe2 (aq)CHsCOO (aq)Fe2+ (CHscoo)2 (aq) 13] Explain the difference in pH due to the presence of Fe2+ species without doing a pH calculation How does the distribution of Fe2* species (aq, uncomplexed) compare with the (Fe(CHsCO0)2) (aq) in a pond containing sediment. Use the soil-water partition coefficient to explain your answKere C, is the concentration in the sediment and Cw is the concentration in the water phase.

Q1: Explain the difference in pH due to the presence of Fe2+ species without doing a pH calculation.
Q2: How does the distribution of Fe2+ species (aq, uncomplexed) compare with the (Fe(C6H5COO)2) (aq) in a pond containing sediment? Use the soil-water partition coefficient to explain your answer: ?? =??/?? where Cs is the concentration in the sediment and Cw is the concentration in the water phase.

Answer 1

From the Henderson Henderson Hasselbalch equation using the relation The p^H Calculation was done. p^H = p K_a + log [Salt]/[Acid] K_a = 6.5 times 10^- 5 or, p^H = 4.22 + log [.150]/[.050]. or, p^H = 4.22 + .477 = 4.697 Then if F e^2 + is added in to the solution of Benzoic Acid it forms a strong complex and it will rather catch up The Acetate ions present within the media and will further facilitate The extent of dissociation which is in accord with The La - Chatelier principle and This further dissociation will decrease The p^H of The media. The u_f value indicates how well Fe^2 + binds with The Sediment Compared to the water phase, if The Sediment Contains large number of complexing and chelating ligands Ten Fe^2 + will bind with Them Compared to water which is consider to be