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What substance would you add to KF(aq) to form a buffer solution? View Available Hint(s) What substance would you add to to form a buffer solution? HClO NaF NH3 KOH HF KCl

1 Answer

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Answer

HF

Step-by-step explanation

A buffer solution contains a weak acid and its conjugate base. The two species shall have a similar concentration in the solution. It's also possible for a weak base and its conjugate acid to form a buffer solution.

The KF solution already contains large number of
\text{F}^(-) ions. The objective is to thus find its conjugate acid or base.


\text{F}^(-) contains no proton
\text{H}^(+) and is unlikely to be a conjugate acid. Assuming that
\text{F}^(-) is a conjugate base. Adding one proton to
\text{F}^(-) would produce its conjugate acid.


\text{H}^(+) \; (aq) + \text{F}^(-) \; (aq) \rightleftharpoons \text{HF}\; (aq)

Therefore
\text{HF} is the conjugate acid of
\text{F}^(-).
\text{HF} happens to be a weak acid. As a result, combining
\text{F}^(-) with
\text{HF} would produce a solution with large number of both the weak acid and its conjugate base, which is a buffer solution by definition.

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