The pH of 0.10 M acetic acid (Ka = 1.8\times10^{-5}) is approximately

2.87 (≈ ½(pKa − log C)) Approximation: [H^+] \approx \sqrt{Ka C} = \sqrt{(1.8\times10^{-5})(0.10)} = 1.34\times10^{-3}. pH = 2.87.

Weak Acid and Base Equilibria

AP Chemistry· difficulty 4/5

K_a = 1.8\times10^{-5}

Explanation

[H^+] \approx \sqrt{K_a C} = \sqrt{(1.8\times10^{-5})(0.10)} = 1.34\times10^{-3}

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