lecture06 - Lecture 6 Moles The Composition of Compounds...

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1 Lecture 6 Moles The Composition of Compounds The law of definite proportions states that a specific chemical compound obtained from any source always contains the same proportion by mass of its elements. H + + OH - ---> H 2 O (2:16) 2 H 2 + O 2 ---> 2 H 2 O (2:16) This means that compounds are not simple mixtures ± Isotopes can vary this somewhat ± Doesn’t apply to many polymers
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2 Chemical Equations Transformation of a Set of Substances to another Set ± Recipe for change is a chemical equation ± Reactants Products Chemical Reactions rearrange Atoms Some Reactions are named ± Example: a combustion reaction Can’t easily measure individual particles ± Connect atomic and laboratory scales Chemical Reactions
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3 Dimensional Analysis ; unit conversion Most numbers have associated UNITS Salary=16. ± Is that dollars/hour, or thousands of dollars per year?? ± Or pesos/yen/pennies??? • Units can help you SOLVE PROBLEMS. 1. What are the units of the unknown? 2. What are the units of the knowns? 3. What type of equation or conversion do I need to get from 1 to 2? Example of dimensional analysis How many eggs are in 3 dozen? ± 12 per dozen- but do we multiply or divide by 12? 3 dozen * = 36 eggs 12 eggs 1 dozen
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4 Inconvenient to measure each item in a large sample ± How many Froot Loops are in a box ? ± How many sugar crystals in a packet ? ± How many particles in a cup of flour? Atoms are small and plentiful “You have a choice between a doughnut and a cereal,” Dr.
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This note was uploaded on 11/18/2011 for the course CHE 131 taught by Professor Kerber during the Spring '08 term at SUNY Stony Brook.

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lecture06 - Lecture 6 Moles The Composition of Compounds...

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