Question

More good buffers. One liter of a buffer is prepared consisting of 100 mM HEPPS at pH 8.0. What is the concentration of the protonated form of HEPPS in this solution?

Answer 1

The concentration of the protonated form of HEPPS -HHEPPS- is:

50mM

Step-by-step explanation:

HEPPS is a buffering agent used in biology and biochemistry. The pKa of HEPPS is 8.00. To solve this problem it is necessary to use Henderson-Hasselbalch formula:

pH = pka + log
`([A^-])/([HA])`

Replacing:

8,0 = 8,0 + log
`([HEPPS^-])/([HHEPPS])`

1 =
`([HEPPS^-])/([HHEPPS])` (1)

The concentration of the buffer is:

100mM = [HEPPS⁻] + [HHEPPS] (2)

Replacing (2) in (1) you will obtain:

[HHEPPS] = 50 mM

And:

[HEPPS⁻] = 50 mM.

Thus, the concentration of the protonated form of HEPPS -HHEPPS- is:

50mM

I hope it helps!