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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 47b

Determine the empirical formulas of the compounds with the following compositions by mass: b. 21.7% C, 9.6% O, and 68.7% F

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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 21.7 grams of C, 9.6 grams of O, and 68.7 grams of F.
Convert the mass of each element to moles by dividing by their respective molar masses: \( \text{C: } \frac{21.7 \text{ g}}{12.01 \text{ g/mol}} \), \( \text{O: } \frac{9.6 \text{ g}}{16.00 \text{ g/mol}} \), \( \text{F: } \frac{68.7 \text{ g}}{19.00 \text{ g/mol}} \).
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.
Round the mole ratios to the nearest whole number to get the subscripts for each element in the empirical formula.
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

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is derived from the percentage composition of each element, allowing chemists to understand the basic composition without detailing the molecular structure.
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Mole Concept

The mole concept is a fundamental principle in chemistry that relates the mass of a substance to the number of particles it contains. One mole of any substance contains Avogadro's number (approximately 6.022 x 10²³) of entities, whether they are atoms, molecules, or ions, facilitating conversions between mass and number of particles.
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Percentage Composition

Percentage composition refers to the mass percentage of each element in a compound. It is calculated by dividing the mass of each element by the total mass of the compound and multiplying by 100. This information is crucial for determining the empirical formula, as it provides the necessary data to find the ratio of elements.
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