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Neutralization equations
Acids are substances which produce the hydrogen ion (H+) in solution, and bases produce the hydroxide ion (OH-) in solution. When an acid reacts with a base it is simply the hydrogen ion reacting with the hydroxide ion to produce water:
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H+(aq) + OH-(aq) ⇒ H2O(l) |
This is the ionic equation for all acid-base neutralization reactions. When writing the full equations just balance out the acidic Hs from the acid, with the OHs from the base to make one or more water molecules. What remains is the salt. It helps if your ionic formulae skills are good so that you can check that the formula for the salt is correct.
Some examples follow:
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HCl(aq) + NaOH(aq) ⇒ NaCl(aq) + H2O(l) |
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2HCl(aq) + Ca(OH)2(aq) ⇒ CaCl2(aq) + 2H2O(l) |
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HCl(aq) + NH3(aq) ⇒ NH4Cl(aq)* |
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H2SO4(aq) + 2NaOH(aq) ⇒ Na2SO4(aq) + 2H2O(l) |
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H2SO4(aq) + Ca(OH)2(aq) ⇒ CaSO4(s) + 2H2O(l) |
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H2SO4(aq) + 2NH3(aq) ⇒ (NH4)2SO4(aq)* |
Be careful when dealing with weak acids, not all the hydrogen atoms are acidic. So don't attempt to replace them all:
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CH3COOH(aq) + NaOH(aq) ⇒ CH3COONa(aq) + H2O(l) |
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2CH3COOH(aq) + Ca(OH)2(aq) ⇒ (CH3COO)2Ca(aq) + 2H2O(l) |
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CH3COOH(aq) + NH3(aq) ⇒ CH3COONH4(aq)* |
*It may worry you that there is no water in these equations. However, ammonia is often written as ammonium hydroxide, NH4OH. If you use this in place of the ammonia you will get an equation with water in it.
Try to write balanced equations for the reactions between the following acid-alkali pairs:
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Nitric acid (HNO3) and potassium hydroxide (KOH) |
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Sulfuric acid (H2SO4) and potassium hydroxide (KOH) |
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Nitric acid (HNO3) and barium hydroxide (Ba(OH)2) |
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Nitric acid (HNO3) and ammonia (NH3) |
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Methanoic acid (HCO2H) and sodium hydroxide (NaOH) |
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Methanoic acid (HCO2H) and calcium hydroxide (Ca(OH)2) |
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Phosphoric acid (H3PO4) and potassium hydroxide (KOH) |
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Phosphoric acid (H3PO4) and calcium hydroxide (Ca(OH)2) |
You can check yours answers here.