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How to write an equation to show ionization?

Vinegar is a dilute solution of acetic acid (HC2H3O2). Carbonated water is a solution of carbonic acid (H2CO3). Write equations to show the ionization of each acid when placed into water. Note: both of these acids are weak acids. Weak acids ionize one hydrogen ion at a time if more than one hydrogen found in the chemical formula. Include the states of matter and balance the equations.

1 Answer
Mar 13, 2018


Here's how I would write the equations.


The acidic hydrogen atoms are at the beginning of the formulas. The other hydrogen atoms are not acidic.

The water removes an acidic hydrogen (#"H"^"+"#) from the acid and becomes a hydronium ion (#"H"_3"O"^"+"#).

The acid that has lost the #"H"^"+"# (the conjugate base) then gets a negative charge.

We write the equation as an equilibrium because both the forward and reverse processes are occurring at the same time.

Acetic acid

#"HC"_2"H"_3"O"_2"(aq)" + "H"_2"O(l)" ⇌ "C"_2"H"_3"O"_2^"-""(aq)" + "H"_3"O"^"+""(aq)"#

Carbonic acid

Carbonic acid ionizes in two steps.

#"H"_2"CO"_3"(aq)" + "H"_2"O(l)" ⇌ "HCO"_3^"-""(aq)" + "H"_3"O"^"+""(aq)"#

#"HCO"_3^"-""(aq)" + "H"_2"O(l)" ⇌ "CO"_3^"2-" "(aq)"+ "H"_3"O"^"+""(aq)"#