For a lab experiment, a student needs 250.00 mL of a 150 mM MES buffer (pKa...

For a lab experiment, a student needs 250.00 mL of a 150 mM MES buffer (pKa = 6.27) at pH 6.50. The student is given solid MES base (MW = 217.22 g/mol), 1.25 M HCl, and 1.25 M NaOH. Describe how the student should make this buffer (including amounts to weigh or measure out). (show all your work)

Expert Solution

Solution.

According to the Henderson-Hasselbach equation,

Plug in the problem statement values:

The solution of this system of simultaneous equation is:

To produce this amount of acid (n=cV), 0.0555*0.25 = 0.0139 moles of HCl required, it corresponds to

V = n/c = 0.0139/1.25 = 0.01112 L, or 11.12 mL.

The amount of the MES base required is n = cV = 0.15*0.25 = 0.0375 moles, and the mass is m=nM = 0.0375*217.22 = 8.146 g.

The buffer should be made according to the following procedure:

8.146 grams of MES base to be weighted and placed into the 250 mL calibrated flask, 11.1 mL of HCl added using a burette, and the distilled water sould be added up to the 250 mL mark on a flask.

queen_honey_blossom answered 2 years ago

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