Question

you are preparing a .4M glycine buffer, pH of 10.08. calculate the number of moles of glycine and sodium glycinate in your buffer solution.

Answer 1

You have the molar ratio of the components of the buffer:

n Salt / n Acid = 10 ^ (pH - pKa) = 10 ^ (10.08 - 9.78) = 2

It has:

i) n Salt - 2 * n Acid = 0

ii) n Salt + n Acid = M * V = 0.4 M * 1 L = 0.4 mol

System of equations is applied and you have:

n Salt = 0.27 mol

n Acid = 0.13 mol

The mass of glycine (Acid) and sodium glycinate (salt) is calculated:

m glycine = n * MM = 0.13 * 75.07 = 9.76 g

m glycinate = 0.27 * 160.04 = 43.21 g

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