Name: __________________________ Class: ____________________ Date: _____________ Written by James Dauray http://www.aurumscience.com Page 1 Empirical Formula Introduction When a chemist is studying an unknown substance, it is possible to do a chemical analysis determining the percent composition of each element that makes up the substance. This percent composition can then be used to find the actual empirical formula of the compound. The empirical formula is the simplest possible ratio of elements within a compound. For example, let’s say that an unknown compound is analyzed and determined to have the following components: 32.38% sodium, 22.65% sulfur, and 44.99% oxygen. The first thing we should do is assume we have exactly 100g of the substance. This would mean that we have 32.38g sodium, 22.65g sulfur, and 44.99g of oxygen. In order to figure out the empirical formula, the first step is actually to convert the mass of each element into moles. 32.38g Na x = 22.26g S x = 44.99g O x = Divide each mole value by the smallest number of moles calculated. In this case, we have the least number of moles of sulfur. Round to the nearest whole number. ____mol O _____mol S ⁄ = ____mol Na _____mol S ⁄ = ____mol S _____mol S ⁄ = This is the mole ratio of the elements, and is used to write the actual empirical formula of the compound. What is the empirical formula of this compound? What is the name of this compound?
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Empirical Formula...empirical formula? 3. Find the empirical formula of a compound found to contain 26.56% potassium, 35.41% chromium, and the remainder oxygen. Once you find the compound.
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