Acids and bases neutralise to give a salt and water

1. A base is a substance that neutralises an acid; a soluble base is called an alkali.

2. In neutralisation, an acid reacts with a base to make a salt and water.

   $$acid+base\to salt+water$$

3. Metal oxides and metal hydroxides are bases, so both follow this pattern.

4. Sulfuric acid and copper oxide:

   $$H_2{SO}_4(aq)+CuO(s)\to {CuSO}_4(aq)+H_{2}O(l)$$

5. Hydrochloric acid and sodium hydroxide:

   $$HCl(aq)+NaOH(aq)\to NaCl(aq)+H_{2}O(l)$$

Acids and carbonates also give off carbon dioxide

1. A metal carbonate reacts with an acid to give a salt, water and carbon dioxide.

   $$acid+metal\; carbonate\to salt+water+carbon\; dioxide$$

2. Hydrochloric acid and calcium carbonate:

   $$2HCl(aq)+{CaCO}_3(s)\to {CaCl}_2(aq)+H_{2}O(l)+{CO}_2(g)$$

3. Test the gas by bubbling it through limewater, which turns milky if it is carbon dioxide.

The acid decides the ending of the salt name

1. Hydrochloric acid makes chloride salts.
2. Sulfuric acid makes sulfate salts.
3. Nitric acid makes nitrate salts.
4. The metal in the salt comes from the base, so copper oxide and sulfuric acid give copper sulfate.

Choosing the right base for the salt you want

1. Use a soluble alkali when both reactants are in solution, so the salt can be found by titration.
2. Use an insoluble base, such as a metal oxide or carbonate, when you can add it in excess and filter off what is left.
3. Either route gives the same salt; the choice depends on whether the base dissolves.