Question

the pkas of h2o (conjugate acid of -oh) and h2po4- (conjugate acid of hpo42-) are 15.7 and 6.8, respectively. identify which is the strong base, and which is the weak base. why can these bases be used to separate the compounds in the unknown mixture? how can you use pka values to identify which compounds will be separated from the mixture at each step?

Answer 1

The pKa values of H2O and H2PO4- show that OH- is the stronger base, while HPO4 2- is the weaker base. These differences in base strength can be used in acid-base separation techniques to isolate compounds from a mixture by adjusting the pH.

Step-by-step explanation:

The pKa values of a conjugate acid-base pair can be used to determine the relative strengths of bases and acids. A lower pKa value indicates a stronger acid, and hence, a weaker conjugate base. Conversely, a higher pKa value indicates a weaker acid and a stronger conjugate base. In the case of H2O and H2PO4-, with pKa values of 15.7 and 6.8 respectively, H2O as the conjugate acid of OH- is a much weaker acid, which means OH- is a stronger base compared to HPO42-, the conjugate base of H2PO4-.

The varying strengths of these bases can be harnessed to separate compounds in an unknown mixture through acid-base reactions. At each step of the separation process, the pKa value can guide us to the pH at which specific compounds will protonate or deprotonate, hence allowing their separation based on charge differences.