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Ch.3 - Mass Relationships in Chemical Reactions
Chapter 3, Problem 91c

What are the empirical formulas of each of the following substances? (c) Zircon, a mineral from which cubic zirconia is made: 34.91% O, 15.32% Si, 49.77% Zr

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1
Convert the percentage of each element to grams, assuming you have 100 grams of the compound. This means you have 34.91 grams of O, 15.32 grams of Si, and 49.77 grams of Zr.
Convert the mass of each element to moles by dividing by their respective molar masses: O (16.00 g/mol), Si (28.09 g/mol), and Zr (91.22 g/mol).
Determine the mole ratio of the elements by dividing each element's mole value by the smallest number of moles calculated in the previous step.
If necessary, multiply the mole ratios by a whole number to get the smallest whole number ratio for each element.
Write the empirical formula using the whole number mole ratios as subscripts for each element.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Empirical Formula

An empirical formula represents the simplest whole-number ratio of the elements in a compound. It is derived from the percentage composition of each element in the substance, allowing chemists to understand the basic composition without detailing the molecular structure.
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Percentage Composition

Percentage composition refers to the mass percentage of each element in a compound. To find the empirical formula, one must first convert the given percentages into moles, which involves dividing the percentage of each element by its molar mass, thus determining the relative amounts of each element present.
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Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is crucial for converting between grams and moles, allowing for the calculation of the number of moles of each element in a compound based on its percentage composition, which is essential for deriving the empirical formula.
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