Question

buffered mobile phase for an upcoming nicotine HPLC experiment. 10) For Analytical Chemistry, you need to prepare a *470 and have 1.000 L of a 0.050 M benzoic acid solution. Since you You need to prepare a solution buffered to a pH 4.70 and cide to make your solution via pH adjustment with a standardized 0.20 M do not have any benzoate salts available, you decide NaOH solution you have left over from a previous experiment. Calculate the volume of NaOH solution needed to make this adjustment (10 points)

Answer 1

The molar ratio of the buffer components is calculated:

n Salt / n Acid = 10 ^ (pH - pKa) = 10 ^ (4.70 - 4.76) = 0.9

It has:

1) n Salt - 0.9 * n Acid = 0

2) n Salt + n Acid = M * V = 0.05 M * 1 L = 0.05 mol

System of equations is applied and there is:

n Salt = 0.024 mol

n Acid = 0.026 mol

The NaOH reacts with the acid and forms salt, the volume of NaOH required is calculated:

n NaOH = n * 1000 / M = 0.024 * 1000 / 0.2 = 120 mL

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