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ch4aika [34]
3 years ago
14

Which weak acid would be best to use when preparing a buffer solution with a ph of 9.20?

Chemistry
2 answers:
Murrr4er [49]3 years ago
8 0

Answer:

The acid with about Ka=6.31x10^{-10}.

Explanation:

Hello,

By assuming that the dissociation of a weak acid is:

H^+X^-H^++X^-

From the following equation one computes pKa as long as the concentration of the conjugate base equals the concentration of the acid for this buffered solution:

pH=pKa+Log(\frac{[Conj.Base]}{[Acid]})\\pKa=pH-Log(1)\\pKa=pH=9.2\\Ka=10^{-9.2}\\Ka=6.31x10^{-10}

So the acid will be that with a Ka=6.31x10^{-10} or close since the possible answers are not shown.

Best regards.

wariber [46]3 years ago
6 0

Answer: -

6.31 x 10⁻¹⁰

Explanation: -

The equation for buffer pH

pH = pKa + log \frac{Conjugate Base}{Acid}

If [Conjugate base] = [Acid], then preparing a buffer is best.

Then pH = pKa

pKa = - log Ka

Ka = 10^{-9.2}

= 6.31 x 10⁻¹⁰

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