Buffers. Chem 12A Mrs. Kay. Buffers help maintain a constant pH. They are able to accept small quantities of acids and bases without drastically changing their pH A buffer is composed of a weak acid molecule in equilibrium with its conjugate base and hydrogen ion (H+).
CH3COOH and CH3COONa
CH3COOH < -- > CH3COO- + H+
There will be a shift to the left
Other things (like water and sodium ions) which are present aren't important to the argument.
What is the pH of a buffer that is 0.12 M in lactic acid (HC3H5O3) and 0.10 M of sodium lactate? For lactic acid, Ka= 1.4 x 10-4
Solve for x, x =1.7 x 10-4
pH = - log [1.7 x 10-4] = 3.77
Notice, when you put the value of x into the original equation it makes no difference for your final answer.