An Introduction to Thermodynamics phần 9 ppsx

7/10/07 4- 105

How does this K compare with the K from part a?

c. If 1 atm of HI at 250 C is placed in a vessel and allowed to reach equilibrium with its o

decomposition products at this temperature, what will be the final pressure of HI?

10. The solubility product constant, Ksp 2 , for MgF at room temperature is 7.1 x 10 . Assuming -9

activity coefficients are unity, find the solubility of MgF2

a. in water

b. in 0.01 M NaF solution

Addition of ions to a dilute solution will decrease the values of activity coefficients. Would the

addition of Na SO increase or decrease the solubility of MgF ? 2 4 2

11. Find ∆G for the process of dissolving MgF in water. Is this positive or negative? Explain o

2

why, in terms of what will happen when MgF is added to water. 2

12. The solubility products for barium oxalate at 18 C are given below. o

(A) BaC O ·2 H O 2 4 2 sp K = 1.2 x 10-7

(B) BaC O ·½ H2O 2 4 sp K = 2.2 x 10-7

a. Assuming only (A) is present in the solid phase, find the concentration of Ba ion in ++

aqueous solution in equilibrium with this solid.

b. Assuming only (B) is present in the solid phase, find the concentration of Ba ion in ++

aqueous solution in equilibrium with this solid.

c. Describe what will happen if 1 g of (A) and 1 g of (B) are added to 100 ml of water at

18 C under 1 atm pressure. o

d. How many phases will be present at equilibrium? What are they?

13. The dissociation constant of H S in water solution is 9.1 x 10 . 2

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H S ----- H + HS 2

+ -

(The second dissociation, to give S , can be ignored here.) Find the concentration of hydrogen =

ion in 0.1 M H S solution. 2

14. The dissociation constant of benzoic acid is 6.30 x 10 at 25 C. Find the concentration of -5 o

hydrogen ion

a. in 0.001 M benzoic acid solution

b. in solution containing 0.001 M benzoic acid plus 0.01 M sodium benzoate. (Benzoic acid

dissociates to give one hydrogen ion, BH ----- B + H .) - +

15. For the cell

Zn/Zn (a = 0.01)//Ag (a = 0.5)/Ag ++ +

a. Write the over-all cell reaction.

b. What is E ?

o

c. What is E ?

d. Is the reaction spontaneous?

16. Find the equilibrium constant for the reaction, at 25 C, o