Question

True/ False: The pH of a soln that is 0.20 M CH3COOH and 0.20 M CH3COONa should be higher than the pH of a 0.20 M CH3COOH soln

Would it be true since CH3COOH and CH3COONa are both weak acids, and if you mix them together, it becomes more diluted, and hence should have a higher pH than just simply CH3COOH?

Answer 1

I didn't work it out. I think it is true, too, but not for the reasons you gave. The acid by itself has a certain pH. The mixture consists of a weak acid (acetic acid) and its salt(the sodium acetate which by the way is a base); therefore, this is a buffered solution. Most, if not all, buffered solutions have a higher pH than the pure acid. I worked it out very quick estimates. The pH of the buffer is 4.74 and the pH of the acid alone is about 2.7.