How does altering the ratio of monosodium to disodium phosphate affect the buffer pH?

The pH of a buffer system is determined by the ratio of the concentrations of its acidic and basic components according to the Henderson-Hasselbalch equation, which states:

[ pH = pK_a + \log\left(\frac{[A^-]}{[HA]}\right) ]

In this context, monosodium phosphate (the acidic component) and disodium phosphate (the basic component) form a buffer. When the ratio of monosodium to disodium phosphate is altered, the balance between the acidic and basic components of the buffer changes, directly influencing the pH.

Increasing the concentration of monosodium phosphate relative to disodium phosphate will increase the amount of the acidic component in the buffer system, leading to a decrease in pH. Conversely, an increase in disodium phosphate relative to monosodium phosphate would result in a higher pH, as there would be more base (the conjugate base component).

Thus, choosing to increase the proportion of monosodium phosphate effectively lowers the pH of the buffer solution. This principle reflects the essential functioning of acid-base buffers: they resist changes in pH upon addition of small amounts of acids or bases, but significant alterations in the ratio of their components result in a noticeable change in