Applications Of Aqueous Equilibria

Question 1

Common Ion Effect - Le Chateleier principle

Answer 1

• adding another substance with an ion in the equilibrium expression will cause a rxn to shift according to Le chatelier principle
• shift favors the solid or deionized form
  See notes

Question 2

Common ion effect - qualitative effect on ph

Answer 2

• decreases solubility of a solute
• adding more conjugate ions may shift the ph
  See notes

Question 3

Buffering capacity

Answer 3

• the capacity in which a buffer can weaken the effect of H+ or OH- ions to resist change in a rxn
• larger [HA] and A- = larger buffering capacity
• [HA]=A- for best buffering capacity in both directions
  pH=pKa+log([base]/[acid])
  [base]=[acid])=1 log(1)=0

Question 4

Henderson-Hasselbach equation

Answer 4

pH=pKa+log([conj.base]/[conj.acid])
pH=pKa+log([A-]/[HA])

Question 5

Henderson-Hasselbach limitations

Answer 5

• soln needs to be buffered (if not use ICE table)
• assumes NO ionization of HA & A
• only a good assumption if enough of Conj so that common ion effect shuts down ionization in both directions

Question 6

Solubility product & solubility

Answer 6

Solubility: max amt of solute to the soln can hold under the given conditions
(molar solubility=max molarity possible)

Solubility product (constant): Ksp, equilibrium constant for the dissolution of an ionic solid
Ksp=[A]^a[B]^b

Question 7

Comparing solubilities of 2 different ionic solids

Answer 7

• can always compare solubilities to see which is more soluble
• you can only compare Ksp values IE dissociates into the same #s of ions so that the relationship between Ksp & X are the same
  See notes

Question 8

Points on a titration curve

Answer 8

See notes
Check if it is buffered, what is the determined pH of the soln, and how to calculate the pH
Zero point, 1/4 point, 1/2 point, 1st eq pt, 2nd 1/2 eq pt, 3/4 between 1&2 eq pt, 2nd eq pt, pH at flattened at pt after 2nd eq pt