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Which weak acid would be best to use when preparing a buffer solution with a pH of 9.80?A. An acid with Ka = 7.9 times 10-12.B. An acid with Ka = 2.0 times 10-5.C. An acid with Ka = 2.5 times 10-7.D. An acid with Ka = 1.6 times 10-6.E. An acid with Ka = 2.0 times10-8.F. An acid with Kg = 1.3 times 10-10.

Respuesta :

Answer:

An acid with Kg = 1.3 times 10-10.

Explanation:

The formula for pH of a buffer solution is as follows

pH = pKa + log [ A⁻ ] / [ HA ]

HA is acid concentration and A⁻ is concentration of conjugate base .

Generally the the second term is very small so neglecting this figure

pH = pKa

9.8 = pKa

If Ka = 10⁻¹⁰ x 1.3

pKa = - log ( 10⁻¹⁰ x 1.3 )

= 10 - log 1.3

= 9.8 approx .

Hence option F is correct .

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