Question

Acetic acid (CH_3COOH) is a weak acid.
a) Write the symbolic equation showing the ionisation of acetic acid.

b)Given that an acetic acid solution of pH 4.8 has a hydrogen ion concentration of 1.58 * 10^-5 mol L^-1, what is the concentration of the acetate ion at equilibrium?

c) Calculate the equilibrium concentration of the undissociated CH_3COOH if the equilibrium constant for this dissociation is 1.8 * 10^-5

Answer 1

a. acetic acid is HAc to save typing.
HAc + H2O ==> H3O^+ + Ac^-

b.
Convert pH = 4.8 to H3O^+. Since the answer to a shows 1 Ac to 1 H3O, then H3O = Ac

c.
Write Ka expression for HAc. Substitute H3O^+ and Ac^- and solve for (HAc).

Post your work if you get stuck.