Chapter3_1[1]

Chapter3_1[1] - 9/5/2011 CHEMISTRY 1307 Chapter III...

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9/5/2011 1 1 CHEMISTRY 1307 Chapter III Chemical Reactions 2 Chemical Reactions A chemical reaction is a process by which one or more substances ( ) are transformed into different ones ( ), with different properties. Reaction of Al + Br 2 3 Chemical Reactions Evidence of a chemical reaction: • Gas Evolution • Temperature________ • _________________ • Precipitation (insoluble species forms) • A flame is produced
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9/5/2011 2 4 Chemical Equations Reactants ________ Chemical Equations show: the reactants and products in a reaction. the relative amounts in a reaction. Example: _ Al(s) + _ O 2 (g) _ Al 2 O 3 (s) The numbers in the front are called stoichiometric __________ The letters (s), (g), ( l ) and (aq) are the physical states of compounds. 5 Chemical Equations _ Al(s) + _ O 2 (g) _ Al 2 O 3 (s) This equation states that: 4 Al atoms + 3 O 2 molecules react to form 2 formula units of Al 2 O 3 or. .. 4 moles of Al + 3 moles of O 2 react to form 2 moles of Al 2 O 3 6 Moles & Equation Coefficients 4 Al(s) + 3 O 2 (g) 2 Al 2 O 3 (s) The coefficients represent molecules, so we can multiply each of the coefficients and look at more than individual molecules. Al(s) O 2 ( g ) Al 2 O 3 (s) 4 molecules 3 molecule 2 molecules
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9/5/2011 3 7 The Law of Mass Conservation Lavoisier, 1788 Let’s test: 4 Al(s) + 3 O 2 (g) → 2 Al 2 O 3 (s) 4 mol Al + 3 mol O 2 2 mol Al 2 O 3 4 (27 g) + 3 (32 g) 2 (102 g) 108 g + 96 g 204 g 204 g = 204 g The mass of the reactants is equal to the mass of the product! Mass is _________. The law of conservation of mass states that mass is neither ________ nor _________ during a chemical reaction. 8 Balancing Chemical Reactions Steps in balancing a chemical reaction using coefficients: 1. Write the equation using the formulas of the reactants and products. Include the physical states (s, l , g, aq etc…) 2. Balance the compound with the most elements
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Chapter3_1[1] - 9/5/2011 CHEMISTRY 1307 Chapter III...

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