2. Buffer capacity refers to the amount of acid or base a buffercan “absorb” without a significant pH change. It is governed by theconcentrations of the conjugate acid and base forms of the buffer.A 0.5 M buffer will require five times as much acid or base as a0.1 M buffer for given pH change. In this problem you begin with abuffer of known pH and concentration and calculate the new pH aftera particular quantity of acid or base is added. In the laboratoryyou will carry out some stepwise additions of acid or base andmeasure the resulting pH values.

Starting with 60 mL of 0.50 M phosphate buffer, pH=6.83, you add1.7 mL of 1.00 M HCl. Using the Henderson-Hasselbalch equation withpK2 for phosphate of 6.64 calculate the following values tocomplete the ICE table.

What is the composition of the buffer to begin with, both interms of the concentration and the molar quantity of the two majorphosphate species? (Units required.)

What is the molar quantity of H3O+ added as HCl, and final molarquantity of HPO and H2PO4- at equilibrium?

What is the new HPO42-/H2PO4- ratio, and the new pH of thesolution?(Note: you can use the molar ratio rather than theconcentration ratio because both species are in the samevolume.)

Now take another 60 mL of the 0.50 M pH 6.83 buffer and add 3.7mL of 1.00 M NaOH. Using steps similar to those above, calculatethe new pH of the solution.