9. Hydrates Some ionic compounds release water when heated. The water molecules are loosely bonded within the solid crystal at regular intervals. Ex: Na2CO3 • 10 H2O is sodium carbonate decahydrate The “ • “ indicates a weak bond between the Na2CO3 and the ten water molecules. First part of compound named according to IUPAC rules. Second part is the number of water molecules using the prefix system. Try These CuSO4•5H2O Ca(NO3)2•3H2O manganese (II) chloride tetrahydrate zinc sulphate heptahydrate 10. Other Commonly Named Chemicals and Formulas Common names are often used chemistry. IUPAC Name Sodium bicarbonate Dinitrogen monoxide Sodium thiosulphate Nitrogen trihydride Formula NaHCO3 N2O HCl(aq) Na2S2O3 H2O Common Name baking soda laughing gas muriatic acid hypo