Question

1. We want to make 250 mL of a 0.1 M phosphate buffer at pH 7.4.
   1. Given that the relevant pKa for phosphate is 7.2, useHenderson-Hasselbalch to calculate the ratio[HPO₄^2?]/[H₂PO₄^?].
   2. The total concentration of the buffer is the sum of the twocomponents, such that

2. [phosphate buffer] = [HPO₄^2?] +[H₂PO₄^?]

   Since we want to prepare a 0.1M buffersolution. If we rearrange the above expression to solve for theconcentration of the acid and plug this into the ratio solved forin problem #1, we can solve for the concentration of the base. Whatis the concentration of the base required in our buffer to get ourdesired pH?

3. What is the concentration of the acid required in our buffer toget our desired pH?
4. If we want to prepare this buffer by mixing already preparedsolutions of 0.1M Na₂HPO₄ and 0.1MNaH₂PO₄, determine the volumes of each bufferrequired to make 250 mL of our 0.1M phosphate buffer of 7.4.(realize that if you mix these two solutions, and the concentrationof the buffer is equal to the sum of the acid + base, you willSTILL have a 0.1 M solution of buffer!)