# L11 - Sextillion Reaction Stoichiometry STOICHIOMETRY from...

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1 Lecture 11 602 Sextillion: Reaction Stoichiometry Key Idea: Balanced chemical equations keep track of rearrangements of atoms. STOICHIOMETRY from the Greek words stoikheione ("element") and metri ā ("measure”) 2A 2 + B 2 2A 2 B * Atoms of elements react in constant ratios. * Atoms are neither created nor destroyed. B B B B B B B B B B B B STOICHIOMETRY 2 H 2 (g) + O 2 (g) Æ 2H 2 O (g) * Atoms of elements react in constant ratios. * Atoms are neither created nor destroyed. Balloon #1: Balloon #2: What is leftover? Tan atoms are in excess Blue molecules are called the limiting reactant * How do you measure exact amounts? * Can you really follow a few atoms and molecules? In cutting-edge experiments!! * What can you do in the lab now? Getting quantitative! Smallest mass measured on a typical laboratory scale: Mass of a single sucrose molecule: 0.000000000000000000000568 g Need a “Nano-Macro” Connection (i.e., a scaling factor ) 0.001 g Mass of a single oxygen molecule: 0.000000000000000000000053 g Getting quantitative! 602,000,000,000,000,000,000,000 = 6.02 x 10 23 12 g 12 amu carbon atoms 602,000,000,000,000,000,000,000 = 6.02 x 10 23 1 g 1 amu hydrogen atoms 602,000,000,000,000,000,000,000 = 6.02 x 10 23 40 g 40 amu calcium atoms 12 30 g 2.5 g pennies 12 6 g 0.50 g paper clips 12 0.26 g 0.022 g rice Number of pieces in measured mass Measured mass Mass of 1 piece Substance MEASURING AMOUNTS OF MATTER? Number... Mass? Volume?

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