# chem 105-2 - Stoichiometry and Balanced Chemical Equations...

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Stoichiometry and Balanced Chemical Equations: Balanced Chemical Equations :  An equation that shows the identities and quantities of  elements/compounds used in a reaction 1.  Things to know a. Atoms and Mass are conserved.  If there are 3 moles of hydrogen on the  reactants side, there need to be 3 moles on the products side b. The numbers in front of the compounds (stoichiometric coefficients, SC) are  not the same for every compound in the reaction c. A formula shows the fixed ratio of elements in a compound, so adjusting the  subscript instead of using an SC would mean that you are changing the  compounds involved in the reaction  2.  How to make it happen a. Ping-pong method: make the numbers match up on both sides by picking a  starting point and “bouncing” between sides b. If you get a non-integer SC, multiply the whole equation out (scalar  multiplication) to achieve an integer answer c. Use the smallest whole number coefficients possible 3.  Things to keep in mind a.  The SC is in MOLES, not grams or atoms Stoichiometry : The relationship between mass-moles-atoms in chemical formulas/reactions 1.  Mass a. Measured in grams b. Mass=moles(formula weight);

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2.  Moles a.  The amount contained in one formula unit of a given substance b. Ex: 1 mol of Nitrogen weighs 14 g (its formula weight) and contains
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• Fall '08
• Kenney

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