Question

What is the pH of 50 mL of Distilled Water mixed with 0.5 g of Zinc (using red litmus paper)?

Whati s the pH of 50 mL of 5 mL of 5 M HCl mixed with 0.5 g of Zinc (using red litmus paper)?

What is the pH of 5 mL of 1 M Copper (II) Sulfate mixed with 0.25 g of Zinc (using red litmus paper)?

What is the pH of 2 mL of 0.1 M Zinc Acetate mixed with 2 mL of 0.1 M Sodium Phosphate (using red litmus paper)?

Answer 1

What is the pH of 50 mL of Distilled Water mixed with 0.5 g of Zinc (using red litmus paper)?

Zinc is not that soluble in water, therefore, expect pH to remain that of pure water, pH = 7

Whati s the pH of 50 mL of 5 mL of 5 M HCl mixed with 0.5 g of Zinc (using red litmus paper)?

mol of Zn = mass/MW = 0.5/65.4 = 0.00764

mol of HCl = MV = 5*5*10^-3 =  0.025

Zn + 2H+ = H2 + Zn+2

H+ left after reaction = 0.025 - 2*0.00764 = 0.00972 mol of H+

[H+] = mol/V = (0.00972)/(50*10^-3) = 0.1944

pH = -log(0.1944 )

pH = 0.71

What is the pH of 5 mL of 1 M Copper (II) Sulfate mixed with 0.25 g of Zinc (using red litmus paper)?

pH = 7, since Cu+2 + Zn(s) = Zn+2 + Cu(s) forms, no effect in H+

What is the pH of 2 mL of 0.1 M Zinc Acetate mixed with 2 mL of 0.1 M Sodium Phosphate (using red litmus paper)?

Zn(acetate)2 + Na3PO4

Zn+2 + 2acetate- + 3NA+ + PO4-3

note that this wforms:

Zn3(PO4)2

mol of Zn = mass/MW = 0.1*2*10^-3 = 0.0002

mol of PO4-3 = MV = 0.1*2*10^-3 = 0.0002

PO4-3 limits

then ,

acetate ion is left at the end

pH = 8.5 approx for acetate ion hydrolysis