Question

Part A

Which of the following buffer systems would be the best choice to create a buffer with pH = 7.1?

Answer :HClO/KClO

Part B

For the best system, calculate the ratio of the masses of the buffer components required to make the buffer.

Express your answer using two significant figures.

Answer 1

A)

if ph goal = 7.1

choose an acid with a pKa vlaue near that

The pKa nearest to 7.1 is HClO (monoprotic acid)

then

pH = pKa + log(ClO-/HClO)

B)

pKa = 7.53 for HClO

so

7.10 = 7.53 + log(ClO-/HClO)

assume: ClO- comes from NaClO

so

10^(7.10-7.53) = NaClO/HClO

0.3715352*[HClO] = [NaClO]

note that:

we can assume this per liter so

0.3715352 * mol of HClO = mol of NaClO

for 1 mol of NaClO = 74.44 g

for each 74.44 g of NaClO = 0.3715352 * 52.46 = 19.490736 g of HClO must be added