Calculate the standard Gibbs energy of reaction and the equilibriumconstant at 2

Question

Calculate the standard Gibbs energy of reaction and the equilibriumconstant at 25°C for the following reactions: 4. (a) (b) Fe3+ + 3OH-Fe(OH)3(s) Ca2+-+ SOA + 2H20CaSO4·2H20(s) 5. A) Calculate AGp for the dissolution of ferrous hydroxide [Fe(OH)2(s)] into Fe+ and OH ons B) If an ideal solution containing 2 mg/L Fe?+ and 10 mgL of the solid is at pH 7.0, in which direction will the reaction proceed? Fe (OH), (s) Fe2+ + 2 OH- 6. Consider systems where the following reactions are occurring under the conditions indicated

Explanation / Answer

Answer:

4). G = 2.303RT*pKa

R = 8.314 J

T = 298K

pKa of Fe+3 = 2.83

G = 2.303*(8.314)*(298)*(2.83)

= 7011.52 J

R = 8.314 J

T = 298K

pKa of Ca+2 = 2.43

G = 2.303*(8.314)*(298)*(2.43)

= 6020.5 J

5). Using G values and equlibrium constant values G* values can be determined.

G = G* + RTlnK

G* = G - RTlnK

6).

(i). H2PO4- HPO4-2 + H+

K = [ H+][HPO4-2 ]/[H2PO4-]

pH = -log[ H+]

7 = -log[ H+]

H+ = 10-7

K = [10-7][5*10-3]/[10-3]

K= 5*10-7

G=--2.303RTlogK

=-2.303*8.314*298*log(5*10-7)

=-5705.8*[log5-7log10)

=-5705.8*(0.6989-7)

=-5705.8*(-6.301)

G =35952.4 J

Similar procedure to be followed for 6 (ii) and 6 (iii).

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