Identifying Acid-Base Reactions
- Acid-Base reactions involves the transfer of one or more protons between chemical species
- Acids are species that donate protons
- Bases are species that accept protons
- In the example below, HCl acts as an acid because it donates one proton to H2O which acts as a base
- Since HCl is just able to transfer one proton, it is a monoprotic acid
HCl (aq) + H2O (l) → H3O+ (aq) + Cl– (aq)
- There are acids that have the capability of donating more than one proton
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- Acids that are able to transfer two protons, are diprotic acids
H2SO4 (aq) + 2H2O (l) → 2H3O+ (aq) + SO42– (aq)
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- Acids that are able to transfer three protons, are triprotic acids
H3PO4 (aq) + 3H2O (l) → 3H3O+ (aq) + PO43– (aq)
Neutralization
- One of the most common acid-base reactions is neutralization
- Neutralization occurs when an acid reacts with a base/alkali to produce salt and water
- The salt produced in the neutralization is formed from the cation of the base and the anion from the acid
- Therefore the name of the salt can be predicted from the acid and base that have reacted
- The cation and the anion the produce the salt are spectator ions
Acid reacted and salt produced
Acid Reacted |
Salt produced |
Hydrochloric acid |
Chloride |
Nitric Acid |
Nitrate |
Sulfuric acid |
Sulfate |
Diagram showing an acid-base neutralization
Neutralization reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) and their respective ionic equations to produce water (H2O) and sodium chloride (NaCl)
Neutralization with gas formation
- The reaction of an acid and a metal carbonate or a metal hydrogen carbonate is also a neutralization reaction
- The products in both case are salt, water and carbon dioxide
- Carbon dioxide is the product in gas state
- Examples for both cases are shown below:
acid + metal carbonate → salt + water + carbon dioxide
2HNO3 (aq) + CuCO3 (s) → Cu(NO3)2 (aq) + H2O (l) + CO2 (g)
acid + metal hydrogen carbonate → salt + water + carbon dioxide
HCl (aq) + NaHCO3 (s) → NaCl (aq) + H2O (l) + CO2 (g)