Ka for acetic acid?

What is the Ka (acid dissociation constant) for acetic acid?

For acetic acid (CH3COOH), the acid dissociation constant (Ka) is commonly given as about 1.8 × 10⁻⁵ at 25 °C. [1]

Why does Ka for acetic acid depend on conditions?

Ka is temperature-dependent because it’s derived from the equilibrium:
CH3COOH ⇌ H⁺ + CH3COO⁻.
Different references (and different temperatures like 0 °C vs 25 °C) report slightly different Ka values, even though they describe the same acid dissociation process. [1]

How does Ka relate to pKa for acetic acid?

Because pKa = -log10(Ka), the Ka value above corresponds to a pKa of about 4.74 at 25 °C. [1]

What’s the corresponding Kb for acetate (the conjugate base)?

If you need the base dissociation constant (Kb) for acetate (CH3COO⁻), it can be found using:
Ka × Kb = Kw (where Kw ≈ 1.0 × 10⁻¹⁴ at 25 °C).
Using Ka ≈ 1.8 × 10⁻⁵ gives Kb ≈ 5.6 × 10⁻¹⁰ at 25 °C. [1]

Sources

1. https://en.wikipedia.org/wiki/Aceticacid#Equilibriumand_thermodynamics