A. What combination of a molecular base (i.e. a neutral compound not an ion!) an

Question

A. What combination of a molecular base (i.e. a neutral compound not an ion!) and a salt of the conjugate acid of the molecular base should you select to prepare a buffer solution that would maintain a pH of approximately 9.80? For full credit, explain your choice (in a simple, straightforward manner)

B. What ratio of concentrations of the conjugate acid and molecular base you selected in part a of this problem would be necessary to achieve a pH of exactly 9.80?

C. Describe, using one well-written sentence, a simple and practical way to make 1.00L of the buffer solution you have defined in parts a and b of this problem. Assume that a 1.0 M solution of the molecular base is available and that the chloride salt of the conjugate acid is available as a pure solid. Note: Even if you have not had a lab course you should be able to provide more details than the number of moles to combine.

Explanation / Answer

A. To prepare a buffer of pH 9.80 we would use the following combination,

we know,

pH = pKa + log[A-]/[HA]

So the base which would have a pKa value closest to the required pH of buffer would be an ideal choice for preparation of the buffer.

Thus, Me3N is the base we would be using. It has pKa 9.80

Combination for buffer would be thus,

M3N/Me3NH+

B. The ratio we would choose for getting a pH of conjugate acid and molecular base would be, 1:1.

C. To prepare a 1.00 L buffer solution, with 1.0 M base we would be using 1.0 M acid solution and combine then to form 1.0 M of salt. The resulting pH would be thus, 9.80.

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