Chem Unit 10: MonoDi-TriPoly-Protic Acids

Say Whhhhhhhhatt?

The Latin prefix mono, di, tri, or poly is used to show how many ‘PROTONS’ or simply H+ ions an acid will give up when its dissolved in water.


A Monoprotic Acid can give up or donate 1 and only 1 H+ ion.

Here are some examples of monoprotic acids;

HCl – Hydrochloric acid
HNO3 – Nitric acid
CH3COOH – Acetic Acid, sometimes written HOAc

Let’s write an ionization equation for HCl in water

HCl(aq) +H2O   -> H3O+ + Cl- ( or moresimply written H+ + Cl-)

Q: Write the ionization equations for Nitric and Acetic Acids.

Here are some examples of diprotic acids;

H2SO4 – Sulphuric acid
H2SO3 – Sulfurous acid

H2CO3 – Carbonic acid ( in soft drinks due to CO2 being dissolved in water. Carbonic acid plays an important part in our body’s blood and respiration system as This is how carbon dioxide dissolves in the blood and is taken back to the lungs to be exhaled.

H2C2O4 – Oxalic acid (driveway, concrete cleaner, wood bleach)

H2S – Hydrogen Sulfide – highly poisonous – smells like rotten eggs ( oh yeah, break open a rotten egg some time and see how it smells)  Hold your nose closed AND RUN!!!!!!  Also an atmospheric  pollutant caused by Sulfur in gasoline from low quality high sulfur crude oil.


Let’s write the ionization equation for a diprotic acid. This time since there are 2 hydrogens released, we need to do this in 2 steps.

Step 1:   H2SO4(aq) +  H2O  –>  HSO4-  +  H3O+  ( or more simply HSO4- + H+)

Step 2:  HSO4(aq)- +  H2O  <–>  SO4–  +  H3O+  ( or more simply HSO4– + H+).

Note that step 2 is not as energetically favorable so the arrows point both ways.


Now you write the ionization equations for H2SO3,  H2CO3, H2CO4, and H2S.

Next we’ll list some triprotic acids.  As a challenge, you should try to write the 3 step ionization formulas.

H3PO4 – phosphoric acid

C6H8O7 – citric acid



Start at the 2:00 minute mark.