Why is sodium hydrogen carbonate also called (sodium) bicarbonate?

Answer

Dear Mark,

In chemistry, the same product is often given different names. These can often be divided into ‘trivial’ names given for various reasons (e.g. because the substance was already known and widely used before structure elucidation, or because the structural name is too complex in day-to-day use), and more ‘systematic’ names that comply with clear rules and describe the structure of the molecule, the rules drawn up by the organization IUPAC (‘International Union of Pure and Applied Chemistry’) being the most commonly used. In the first case the name alone is of little use and you will have to look up what exactly is meant by it, while with a systematic name the name alone will suffice. The disadvantage of the structural names, on the other hand, is often that they can be very long, especially for more complex molecules, and are therefore not convenient to use.

Bicarbonate is the trivial name, sodium hydrogen carbonate the systematic. ‘Bicarbonate’ is historical and would come from initial mass analyzes that differentiated sodium carbonate (Na₂CO₃) and sodium hydrogen carbonate (NaHCO₃) showed: per sodium atom there is twice as much mass of carbonate in the second case as in the first case, hence the name bi/two-carbonate.