When microorganisms reproduce they release waste products that may change the pH and prevent further reproduction. Therefore culture mediums for growing microorganisms are usually buffered. The median for the culture of lactobacilli includes a buffer prepared by dissolving 25 grams K2HPO4 and 25 grams KH2PO4 in water and diluting to 250.0 mL. The question is what is the pH of the buffer solution? Before the culture medium is used it is diluted to 1.000 L with distilled water. So then what would be the pH after dilution as well?
A buffer is a solution that contains a weak acid and its conjugate base. It is called a buffer because such a solution resists changes to pH because the acid part of the buffer can react with any base added while the base of the buffer can react with any acid added. Your relevant chemical reaction is as follows:
H2PO4- <---> HPO42- + H+
There are several standard ways to calculate the pH of a buffer solution. One can actually work out the equilibrium problem, but the critical take home lesson about a buffer is this: the pH of the buffer solution ...
The solution explains how to find the pH under different states of the same solution as asked using the relevant theory and forumlae.