Total Solubility/pH of Precipitation

Question 1

Total Solubility

Answer 1

[HA] + [A-]

• [HA] - intrinsic solubility, constant at same temp and solvent
• [A-] - amount of weak acid ionized

Question 2

Total Solubility + pH

Answer 2

• At low pH, total solubility is about equal to [HA]

- At high pH, total solubility is [HA] + [A-]

Question 3

[A-] =

Answer 3

Ka *[HA]/[H3O+]

This makes TS:
[HA][1+ (Ka/H3O+)]

Question 4

Solubility of Weak Acids Equations

Answer 4

• Ka = [H3O+][P-]/[HPsolution]
• *HPsolution = constant
• [P-] = Ka*[HPsolution]/[H3O+]
• Total Solubility: St = [HPsolution] + [P-]
• [P-] = St - [HPsolution] = St - So

Question 5

pH at which precipitation occurs in weak acids…

Answer 5

pHp = pKa + log[(St-So)/So]

Question 6

Solubility of Weak Bases

Answer 6

TS = [B]*[1 +([H3O+]/Ka)]

Question 7

pH at which precipitation occurs in weak bases….

Answer 7

pHp = pKa + log[So/(St-So)]