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Problem 34

Which of the following sets of information allows…

University of Maine

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Problem 33

List three ways compositional data may be given in a problem that involves finding an empirical formula.


1. percent composition
2. masses of each element in a compound
3. combustion analysis



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Video Transcript

The empirical formula is the lowest whole number ratio of moles of element in a compound. So, for example, hydrogen peroxide is a compound that has an empirical formula of H O. What this means is that for every one mole of hydrogen in the compound, there's one mole of oxygen. There are three different ways in which data may be presented to find the empirical formula. The first is that you may be given the masses of each element in a compound, so, for example, grams of hydrogen, grams of oxygen. So to find the empirical formula, take the grams of each element, change them to malls using molar mass, and then find the lowest whole number ratio of the malls and write this as your empirical formula. Sometimes, instead of grams of each element, you're given a percent composition. So, for example, percent of hydrogen percent of oxygen. If you're given percents, the first thing to do is to find the number of grams by assuming you have 100 grams of the total compound. So if you have ah 100 grams of a compound, multiplying it by its percent will tell you the grams of each element you can then change two moles using the molar mass. Find the whole number ratio and then, finally, the empirical formula. The third way in which empirical formula could be determined, is through combustion analysis, and this works for organic compounds containing hydrogen and carbon, and it reacts with oxygen to produce carbon dioxide and water. And using the data before and after the reaction of water, E amounts of carbon, hydrogen and oxygen can be found, which can then be used to find the empirical formula.

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