So for example, suppose we had a system of 0.5 molar of acetic acid mixed with 0.5
molar of sodium acetate in one liter of water, and this PH and this system's PH was 4.74. So now what happens to our PH if we add 0.1 molar of hydrochloric acid, as we did in part A? Well, now our PH will only decrease from 4.74
to 4.72. That's a change of 0.2. That's a very small change. Well, that's because this system has a buffer system.