What is citric acid? How does it ionize?

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Answer 1 · 2015-03-26T16:48:36

See below.

Citric acid is a weak tribasic acid.

It loses the acidic hydrogen atoms in three separate steps.

$H_{3} C_{6} H_{5} O_{7} + H_{2} O ⇌ H_{3} O^{+} + H_{2} C_{6} H_{5} O_{7}^{-}; p K_{a1} = 3.25$ $"H"_3"C"_6"H"_5"O"_7 + "H"_2"O" ⇌ "H"_3"O"^+ + "H"_2"C"_6"H"_5"O"_7^"-"; "p"K_text(a1) =3.25$
$H_{2} C_{6} H_{5} O_{7}^{-} + H_{2} O ⇌ H_{3} O^{+} + {HC}_{6} H_{5} O_{7}^{2-}; l p K_{a2} = 4.77$ $"H"_2"C"_6"H"_5"O"_7^"-" + "H"_2"O" ⇌ "H"_3"O"^+ + "HC"_6"H"_5"O"_7^"2-";color(white)(l) "p"K_text(a2) =4.77$
${HC}_{6} H_{5} O_{7}^{2-} + H_{2} O ⇌ H_{3} O^{+} + C_{6} H_{5} O_{7}^{3-}; m l p K_{a3} = 5.19$ $"HC"_6"H"_5"O"_7^"2-" + "H"_2"O" ⇌ "H"_3"O"^+ + "C"_6"H"_5"O"_7^"3-"; color(white)(ml)"p"K_text(a3) =5.19$