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15. Into a 5.0 liter flask was placed 35.7 g of PCI5 . The flask and contents were heated to 250 0 C, and then held at temperature until the following equilibiurm was established:
	PcI5 (g)<	> Pc13 (g) + Cl2 (g)

It was then shown by analysis that 875 g of Cl2 was pesent in the equilibrium mixture. Calculate K~. (This will be a numerical calculation, not simply the equilibirum expression) (10 points)

1 6. Given that K1 for acetic acid is 1 .8 X 10-5, calculate the percent ionization of 0.5 M acetic acid. (5 points)

1 7. Calculate the concentration of Hydrogen ions in a solution that
Is 0.1 M with respect to acetic acid and 0.2 M with respect to
NaC2H3O2. Use the K1 for acetic acid listed in problem 16.
(Hint: In order to work this problem you will need to remember
how salts compared to weak acids are relatively ionized)
(10 points)

18. The above problem is respresentative of what type of system?