In: Chemistry
Calculate the pH of the solution when the following substances are added together:
20 mL of 0.001 M HCl and 0.5 mL of 0.04 M Sodium Acetate
200 mL of 0.1 M HCl and 8 mL of 2.5 M Sodium Acetate
1)
millimoles of CH3COO- = 0.5 x 0.04 = 0.02
millimoles of HCl = 20 x 0.001 = 0.02
CH3COO- + HCl -----------------> CH3COOH
0.02 0.02 0
0 0 0.02
concentration of CH3COOH = 0.02 / (20 + 0.5) = 9.756 x 10^-4 M
Ka = x^2 / 9.756 x 10^-4 - x
1.8 x 10^-5 = x^2 / 9.756 x 10^-4 - x
x = 1.238 x 10^-4
[H+] = 1.238 x 10^-4 M
pH = -log (1.238 x 10^-4 )
pH = 3.91
similarly do 2nd one also.