Video Transcript
Most carbonate salts are insoluble. Which group of elements do however form soluble carbonate salts?
To answer this question, we must understand the difference between a substance that is insoluble and soluble. A substance that is insoluble cannot be dissolved when added to a solvent. A substance that is soluble can be dissolved in a given solvent. Since the type of solvent is not specified by the question, we can assume it is referring to the salt’s ability to dissolve in water. The substance in question is a carbonate salt. Carbonate is the negatively charged ion CO3 2−, and a salt is an ionic compound made up of cations and anions.
We have been given the anion present in these salts, but we must determine which group of elements will form the cations that will make these salts soluble. To do this, we can reference the water solubility rules, which provide information about many different ions and their solubility in water. For this question, we will focus only on the water solubility rules featuring carbonate. Compounds containing the carbonate anion are insoluble, as indicated by the question. However, there are some exceptions. Carbonate compounds containing also the ammonium ion, lithium ion, sodium, potassium, rubidium, or cesium ions would be considered soluble in water.
If we look to the periodic table, we will find that these five metals, collectively called alkali metals, are found in group one. So an alkali metal cation would form a soluble carbonate salt, for example, sodium carbonate. Therefore, the group of elements that do form soluble carbonate salts is group one metals.
