8E & 8D A base will react with an acid to produce a salt and water. If the base dissolves in water we call it an alkali. Alkalis are slimy to the touch, taste bitter (or soapy) and turn litmus blue. Alkalis have a pH greater than 7. All metal oxides are bases and metal hydroxides that dissolve in water form alkalis.
The table below shows some common alkalis and their approximate pH values (at a standard concentration).
| Base | Common Name | pH (at 0.1 M) |
| magnesium hydroxide | 10 | |
| sodium hydroxide | caustic soda | 13 |
| sodium bicarbonate | baking soda | 8 |
| sodium carbonate | washing soda | 11 |
| ammonium hydroxide | ammonia | 11 |
| calcium hydroxide | limewater | 12 |
The reaction that occurs between an acid and a base (alkali) is called neutralisation. Examples include…
Questions…
- What is the strongest alkali listed on the table?
- The presence of which gas can be shown with limewater?
- Indigestion is caused by a build up of acid in the stomach. Which alkali from the table would make the best remedy for indigestion? Explain your choice.
- What is the common name for calcium sulphate?
- Copper carbonate and calcium carbonate are both insoluble in water. How do we know from the information above that sodium carbonate is soluble in water?
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