The pKa of a certain weak acid is 4.0. Calculate the ratio of proton acceptor to proton donor at pH 7.0.

The ratio of proton acceptor to proton donor is 1000

Explanation:

In a weak acid, the proton donor is HA and proton acceptor is A⁻. Using Henderson-Hasselbalch formula:

pH = pka + log₁₀ [A⁻] / [HA]

7,0 = 4,0 + log₁₀ [A⁻] / [HA]

3,0 = log₁₀ [A⁻] / [HA]

10³ = [A⁻] / [HA]

1000 = [A⁻] / [HA]

That means the ratio of proton acceptor to proton donor is 1000

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