Acetic acid (CH3COOH) reacts with water to form the acetate ion and the hydronium ion: Upper C upper H subscript c upper C upper O upper o upper H (a q) plus upper H subscript 2 upper o (l) double arrow upper C upper H subscript 3 upper C upper o upper O superscript minus (a q) plus upper H subscript 3 upper o superscript plus (a q).

At equilibrium, the concentration of CH3COOH is 2.0 × 10–1 M, the concentration of CH3COO– is
1.9 × 10–3 M, and the concentration of H3O+ is 1.9 × 10–3 M. What is the value of Keq for this reaction?

1.8 × 10–5

5.5 × 104

9.5 × 10–3

1.1 × 102