Answer:
To make the buffer you must add 1 mole of MES in the liter of the buffer.
Explanation:
To find pH of the buffer of MES you must use Henderson-Hasselbalch equation:
pH = pKa + log [MES⁻] / [MES]
Where [MES⁻] is molar concentration of unprotoned MES and [MES] molar concentration of the acid
Replacing:
6.2 = 6.2 + log [1M] / [MES]
Molar concentration of [MES⁻] is 1mol / L = 1M
0 = log [1M] / [MES]
1 = [1M] / [MES]
[MES] = 1M
That means to make the buffer you must add 1 mole of MES in the liter of the buffer
