Ka value for acetic acid?

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

Acetic acid (CH₃COOH) has a Ka of about 1.8 × 10⁻⁵ at 25 °C.

What pKa value corresponds to that Ka?

Acetic acid’s pKa is about 4.74, which matches a Ka near 1.8 × 10⁻⁵.

Does Ka change with temperature or concentration?

Yes. Ka depends on temperature (it’s typically quoted at 25 °C). The concentration of the solution can affect observed acidity (through activity and non-ideal behavior), but the tabulated Ka is the intrinsic thermodynamic constant.

Why do calculators sometimes show slightly different values?

Different references may report Ka using:
- different temperature assumptions (often 25 °C),
- different rounding,
- different activity-coefficient treatments and source data.

If you tell me the temperature (e.g., 20 °C vs 25 °C), I can give the most appropriate Ka value for that condition.