22. Consider a pt. 8.00 solution of Naf, a. Cakculate [F] for this solution Ka-A

Question

22. Consider a pt. 8.00 solution of Naf, a. Cakculate [F] for this solution Ka-A7-10t b. What would be the solubility of Ca, K.-39×101 .inthis sok ion Naf ? c. What would be the pH of this solution if it was hailf-titrated by a strong acd? d. What would be the approximate pht of this solution if it was fully titrated by an equal volume of i valid (in reality it is not, but the pH obtained is very close). acid? Assume that the approximation is 23. BONUS QUESTION. Determine Eall and AG" for the following reaction (10 points): Fe2. (aq)+ Zn(s) Fe(s) + Zr?, (aq) 0.440 v red F2. (aq) +2e- Fe(s) rod Zn2-(aq)+ 2e- Zn(s)

Explanation / Answer

a.

F- for:

NaF <-> Na+ + F-

F- + H2O <-> HF + OH-

Kb = [HF][OH-]/[F-]

pOH = 14-8 = 6

[OH-] = 10^-6

1.47*10^-11 =(10^-6)(10^-6)/(M-10^-6)

M = (10^-6)*(10^-6)/(1.47*10^-11) + 10^-6

M = 0.0680

[F-] = 0.0680 M

b.

Ksp = [Ca+2][F-]^2

3.9*10^-11 = [Ca+2])(0.0680)^2)

[Ca+2] = (3.9*10^-11)/(0.0680^2)

[Ca+2] = 8.434*10^-9 M

S = 8.434*10^-9 M

c

pH of solution in the half way

pOH = pKb + log(HF/F-)

pKB = -log(1.47*10^-11) = 10.83

pOH = pKb + log(1)

pOH = 10.83

pH = 14-10.83 =3.17

d

if fully titrated, the pH will be nearest to pKA

pH = 3.20 approx

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