Select True or False: A mixture made from 10 mL of 1 M HCl and 20 mL of 1 M CH3COONa would be classified as a buffer solution.

True.

Explanation:

There are three ways to make a buffer.

a.  Generating a solution of a weak acid and its conjugate base.

b. Adding to a solution of a weak acid a certain quantity of

strong base, so that the acid remains in excess.

c. adding a limited amount to a conjugate base solution

of strong acid so that the base remains in excess.

We are in c, in this situation.

How do you calculate, pH? We apply Henderson Hasselbach.

pH = pka + log (mmoles base - mmoles acid)/ mmoles acid

pH = pKa + log ((20 ml . 1 M - 1 ml . 10M) / 10 mmoles

pH = 4.76 + log 1 → 4.76 ⇒ pH = pKa