Zn Solubility

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.

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

pH determination pH can be determined from the concentration of H30+ from the following equation: pH=-log[H30+]

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

Or 3.0x1011 * (10-pH)2 = [Zn2+] Or pH = -log ([Zn2+] / 3.0x1011)-1/2

Some figured values are pH 6:.3 M = [Zn2+] pH 7:.003 = [Zn2+] pH 8: 3.0x10-5 = [ Zn2+]

Analyzing Solutions pH= ° 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

pH= ° 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

At Higher Temperatures pH= ° 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.

pH= ° 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.