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A student must make a buffer solution with a pH of 6.5. Determine which of the...

A student must make a buffer solution with a pH of 6.5. Determine which of the acids and conjugate bases listed below are the best options to make a buffer at the specified pH....

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Answer #1

For making best buffer of pH = 6.5 the weak acid pKa should be nearer to pH 6.5

PKa values for phosphoric acid of are 2.16, 7.21 and 12.32. Monosodium phosphate and its conjugate base, disodium phosphate are usually used to generate buffers of pH values around 6.5.

We can determine the exact amount of acid and conjugate base needed to make a buffer of a certain pH, using the Henderson-Hassel Bach equation-

pH= pKa+ log([A−]/[HA])

Where [A-] and [HA] are concentrations of the conjugate base disodium phosphate and starting acid Monosodium phosphate

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