When asked to find examples of three (non-ionic) compounds whose molecular and empirical formulas are the same and three that are different why are ionic compounds excluded?© BrainMass Inc. brainmass.com September 28, 2022, 9:48 pm ad1c9bdddf
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Non-ionic compounds are covalent compounds. As such, the molecular formulas and empirical formulas can be different. However, with ionic compounds, the empirical formula is the same as the molecular formula all the time.
An empirical formula is kind of like the "lowest common chemical denominator" of a compound. That means that the true molecular formula might be a "multiple" of the empirical formula, resulting in a much more complex compound.
On the other hand, all ionic compounds are not really compounds at all. Rather they are made up of a lattice of cations and anions that are arranged in a three-dimensional matrix. Therefore, there isn't really a molecular formula for ionic compounds, as there isn't a molecule. Rather, the formula that we right down is already the "lowest common chemical denominator." An example would be NaCl. This is really a huge three-dimensional lattice or matrix made up of interlinked sodium ions and chloride ions. There aren't separate molecules made up of 1 sodium and 1 chloride. It doesn't exist that way.
But non-ionic compounds are made up of discrete separate molecules. Therefore, the empirical formula can be different than the actual molecular formula. For example, methane -- CH4 -- is one such compound. this is the empirical formula (for it can't be reduced any further), but it's also the actual compound. Therefore, this is also its molecular formula.© BrainMass Inc. brainmass.com September 28, 2022, 9:48 pm ad1c9bdddf>