Molecular substances never ionize in solution, they exist as complete molecules and they NEVER have a charge. Examples include sulfur trioxide (SO 3), carbon dioxide (CO 2), water (H 2O) and glucose (C 6H 12O 6). Molecular compounds involve only nonmetals. It has an ionic bond between the two polyatomics and thus qualifies as an ionic substance. Sometimes a student wonders if a compound between two polyatomics, say NH 4NO 3, is an ionic substance. Remember to never split apart a polyatomic ion. When an ionic substance is dissolved in aqueous solution, it ALWAYS ionizes and the ions always have a charge. Examples are sodium chloride (NaCl), magnesium nitrate and ammonium sulfate. Ionic compounds are between metals and nonmetals or between metals and polyatomic ions. To transform a complete molecular equation to a complete ionic equation, you need to know the difference between an ionic compound and a molecular compound. The word total can also be used, as in 'total ionic equation' or even simply 'total equation.' There is no standard term for this type of equation. Keep in mind that "ℓ" and "aq" mean different things. I have chosen to use "ℓ" to indicate the liquid state, as opposed to the more common "l". You can use words for an ionic equation (either complete or net), it just isn't usually done. Ions (never words) will be used for the complete ionic equation and the net ionic equation, which will follow just below. Only full formulas (never words or ions) are involved in a complete molecular equation. Here are the word equations above, repeated using formulas:īaCl 2(aq) + Na 2SO 4(aq) -> BaSO 4(s) + 2NaCl(aq) This means that you must be able to (1) write correct chemical formulas from the names and (2) balance chemical equations. I started out with names for the complete molecular equations because your first answer in a given problem is often to translate the names into a complete molecular equation equation. (However, when using formulas, the examples used tend be done in a similiar style world-wide.) There is no standard way to arrange a chemical equation using the names of the substances. Sometimes aqueous is never used and the question writer simply assumes you know everything is happening in aqueous solution. The word 'aqueous' could be used as well as 'precipitate.' Sometimes aqueous is used for the reactants, but assumed for the products. The wording in problems like the above can vary somewhat. Here are two examples:īarium chloride solution reacts with sodium sulfate solution to make solid barium sulfate and aqueous sodium chlorideĪqueous solutions of hydrochloric acid and sodium hydroxide react to produce sodium chloride and water Many times, problems of this type will start out with an equation in words. This type of equation shows the full formula for each substance involved (or the full name of each substance), without reference to a substance being ionic or molecular. Or, perhaps, a future lab partner who learned it one way, while you had learned it a different way. You have to know them all (even the one-offs) because you never know what a particular teacher/textbook might use. They are (a) 'empirical equation' and (b) 'non-ionic equation.' In my years of doing chemistry stuff, I have seen two one-off names for what I call the complete molecular equation. These equations can also be called 'complete formula equations,' 'total formula equations,' or simply 'formula equations.' There is no standard name. If you go over there, make sure you ignore the late-1990's style and concentrate on the information. It has a lot of good information, said in a different sequence than I do below. How to Write Ionic Equations is an extensive discussion of the topic. ChemTeam: Equations: Complete Molecular, Complete Ionic and Net Ionic Equations: Complete Molecular, Complete Ionic and Net Ionic Ten Problems Fifteen Problems Twenty-Five Problems All NR Equations & Reaction Types menu
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