Acetic acid has a Ka of 1.8Ã10â5. Three acetic acid/acetate buffer solutions, A, B, and C, were made using varying concentrations: [acetic acid] ten times greater than [acetate], [acetate] ten times greater than [acetic acid], and [acetate]

sln A: pH = 3.745

sln B: pH = 5.745

sln C: pH = 4.745

Explanation:

CH3COOH ↔ CH3COO - + H3O + Ka = ([ H3O + ] * [ CH3COO - ]) / [ CH3COOH ] = 1.8 E-5

sln A:

⇒ [ CH3COOH ] = 10 [ CH3COO - ]

⇒ [ CH3COO - ] / [CH3COOH ] = 1 / 10

⇒ Ka = 1.8 E-5 = [ H3O + ] * (1 / 10)

⇒ [ H3O + ] = (10) * (1.8 E-5) = 1.8 E-4

⇒ pH = - log (1.8 E-4) = 3.745

sln B:

⇒ [ CH3COO - ] = 10 [ CH3COOH ]

⇒ [ CH3COO - ] / [ CH3COOH ] = 10

⇒ Ka = 1.8 E-5 = 10 * [ H3O + ]

⇒ [ H3O + ] = 1.8 E-5 / 10 = 1.8 E-6

⇒ pH = - log (1.8 E-6) = 5.745

sln C:

⇒ [ CH3COO - ] = [ CH3COOH ]

⇒ [ CH3COO - ] / [ CH3COOH ] = 1

⇒ Ka = 1.8 E-5 = (1) * [ H3O + ]

⇒ [ H3O + ] = 1.8 E-5

⇒ pH = - log (1.8 E-5) = 4.745