Balanced Equations and the Mole

The coefficients in a balanced equation can be interpreted as moles of the respective substance. Consider the reaction between methane gas, CH4, and chlorine gas. The balanced equation is  

In a balanced equation, the coefficients equal the number of moles of each substance. Interpreting a balanced equation in terms of moles allows it to be used quantitatively, making it possible to determine the amount of product that forms for a given amount of reactant, or to determine how many grams of one reactant are needed to completely react with a known amount of another. More could be said about this here, but Chapter 8 is devoted to calculations of this type. For now, remember that a balanced equation is a mole statement  

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This is a critical chapter in your study of chemistry. Our goal is to help you master the mole concept. You will learn about balancing equations and the mole/mass relationships (stoichiometry) inherent in these balanced equations. You will learn, given amounts of reactants, how to determine which one limits the amount of product formed. You will also learn how to determine the empirical and molecular formulas of compounds. All of these will depend on the mole concept. Make sure that you can use your calculator correctly. If you are unsure about setting up problems, refer back to Chapter 1 of this book and go through Section 1-4, on using the Unit Conversion Method. Review how to find atomic masses on the periodic table. Practice, Practice, Practice. 

Write the balanced equation and the mole ratio that relates mol O2 to mol MgO. 

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