The content that follows is the substance of lecture 9. In this lecture we cover the relationship between Empirical and Molecular formulas and the calculations used to determine one from the other. The Empirical FormulaAn Empirical formula is the chemical formula of a compound that gives the proportions (ratios) of the elements present in the compound but not the actual numbers or arrangement of atoms. This would be the lowest whole number ratio of the elements in the compound. For Example: In order to determine the Empirical formula for a compound or molecule, we need to know the mass percentages of the the elements in the compound. Once we have this information we can convert it to moles to determine the ratios between the elements. A simple rhyme can be used to remember the process: Percent to Mass Mass to Mole Divide by Small Multiply 'til Whole For Example:
Some more detailed instructions: Here are some practice problems with answers:
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