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Zn Solubility

Investigate the effects of temperature and pH on zinc solubility in ACSF solutions. Analyze precipitation behavior based on zinc chloride concentration. Determine pH levels and observe precipitation patterns at varying temperatures.

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Zn Solubility

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  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=-log[H30+]

  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+] _______ [H30+]2

  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.

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