Zn Solubility

1
Zn Solubility
2
Zn2 in ACSF

• How much ZnCl2 can be added to a solution of ACSF
  at a given temperature before one will observe a
  precipitate.
• What effect does pH have on solutions.

3
Formulas

• Zinc Hydroxide in water.
• Zn(OH)2 (s) ?? Zn2(aq) 2OH- (aq) Ksp
  3.0x10-17
• 2OH-(aq) 2 H30(aq)?? 4H20(l) (K1/w
  1.0x1014)2
• Zn(OH)2(s) H30 (aq)?? Zn2 (aq) 4H20(l)
  
• Knet 3.0x10-17 1.0x1014
  1.0x1014 3.0x1011

4
pH determination

• pH can be determined from the concentration of
  H30 from the following equation
• pH-logH30

5

• From the reaction and the previous equation, the
  amount of Zn2 in solution based on pH can be
  determined from the following equation
• 3.0x1011 Zn2
• _______
• H302

6
Or

• 3.0x1011 (10-pH)2 Zn2
• Or
• pH -log (Zn2 / 3.0x1011)-1/2

7

• Some figured values are
• pH 6 .3 M Zn2
• pH 7 .003 Zn2
• pH 8 3.0x10-5 Zn2

8
Analyzing Solutions

• pH 7.29
• 24 C
• 100 µM
• 0/4 solutions had visible precipitations.
• 200 µM
• 0/4 solutions had visible precipitations.
• 300 µM
• 0/4 solutions had visible precipitations.
• 400 µM
• 0/4 solutions had visible precipitations.
• 500 µM
• 0/4 solutions had visible precipitations.
• 600 µM
• 0/4 solutions had visible precipitations.
• Upon sitting, solutions that contained 400 µM to
  600 µM ZnCl2 showed precipitation at the bottom
  of centrifuge tube.
• pH of solution did not decrease significantly.
  Lowest pH was measured at 7.23

9

• pH 7.19
• 21.6 C
• 300 µM
• 0/3 solutions had visible precipitations.
• 400 µM
• 0/3 solutions had visible precipitations.
• 500 µM
• 0/3 solutions had visible precipitations.
• 600 µM
• 0/3 solutions had visible precipitations.
• Lowest pH was measured at 7.17

10
At Higher Temperatures

• pH 7.29
• 34 C
• 100 µM
• 0/2 solutions had no visible ppt.
• 200 µM
• 0/2 solutions had no visible ppt.
• 300 µM
• 2/2 solutions had visible ppt.
• 400 µM
• 2/2 solutions had visible ppt.
• 500 µM
• 2/2 solutions had visible ppt.
• 600 µM
• 2/2 solutions had visible ppt.
• All of these solutions had been left overnight in
  a water bath at 35 C.

11

• pH 7.19
• 35.3 C
• 300 µM
• 0/3 solutions had visible ppt.
• 400 µM
• 0/3 solutions had visible ppt.
• 500 µM
• 0/3 solutions had visible ppt.
• 600 µM
• 0/3 solutions had visible ppt.
• Solutions had been left standing for
  approximately 1 hour.