Question

What should be the ph of a solution of 5.0 ml of 0.1 M acetic acid and 5.0ml of 0.1M sodium acetate and 40.0ml h20? please show steps

Answer 1

lets find the concentration of CH3COOH after mixing:

[CH3COOH] = M(CH3COOH)*V(CH3COOH) / total volume

[CH3COOH] = 0.1 M * 5.0 mL / (5.0 + 5.0 + 40.0) mL

[CH3COOH] = 0.1 M * 5.0 mL / 50.0 mL

[CH3COOH] = 0.01 M

lets find the concentration of CH3COONa after mixing:

[CH3COONa] = M(CH3COONa)*V(CH3COONa) / total volume

[CH3COONa] = 0.1 M * 5.0 mL / (5.0 + 5.0 + 40.0) mL

[CH3COONa] = 0.1 M * 5.0 mL / 50.0 mL

[CH3COONa] = 0.01 M

CH3COOH and CH3COONa form buffer

pKa of acetic acid = 4.76

use:

pH = pKa + log {[CH3COONa]/[CH3COOH]}

pH = 4.76 + log (0.01/0.01)

pH = 4.76 + log (1)

pH = 4.76 + 0

pH = 4.76

Answer: 4.76