Please SHOW ALL WORK and give explanations. I previously posted this question an

Question

Please SHOW ALL WORK and give explanations. I previously posted this question and someone said more information was needed. This is the only info I was given so if needed I guess somethings may be needed to be looked up. Thanks :)

4. (10 points) The data below are experimentally determined by various authors (see for example Davison et al., 1991) plotted as og (Fez versus pH for amorphous iron sulfide (Fes) at 298 K and p 104 atm. The data with numbers refer to various aged (in H2s hours) iron sulfide precipitate samples. (i) What solubility constant Ksp can be derived for from these data for the reaction: Fes (amorphous solid) 2H Fe2+ H2S(g) (ii) How does the solubility change with age of the precipitated Fes? 750 106 20 A A pH Page 5 of 6

Explanation / Answer

Expression for Ksp = [Fe2+]*pH2S / [H+]2

The point ( 3.7 , 3.4) lies on the graph. ( This is the best approximation I could make from the graph . You can make a better approximation by properly scaling the graph ).

pH = 3.7 means [H+] = 10-3.7

-log [Fe] = 3.4 means [Fe2+] = 10-3.4

Putting values we get:

Ksp = 1

We can see from the graph that data point with time value 750 has a lesser Ksp value as compared to the points 70 ( or even 20 )

Thus as the time of precipitated FeS increases, solubility of FeS decreases.

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