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lecture14%28chapt9%29

# lecture14%28chapt9%29 - Chapter 9 Stoichiometry The...

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1 Chapter 9 Stoichiometry The mole-Ratio method 6.022 X 10 23 molecules 6.022 X 10 23 formula units 6.022 X 10 23 atoms 6.022 X 10 23 ions 1 mole = number of moles = number of molecules 6.022 X 10 23 molecules/mole molar mass = grams of a substance number of moles of that substance molar mass = grams of monoatomic element number of moles of that element

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2 Molar mass : The mass in grams of one mole of any substance. Molar mass = Mass of 1 mole of substance = Mass of 6.022 x 10 23 molecules of substance =Molecular (formula) weight of substance in grams.
3 The word stoichiometry: derives from two Greek words: stoicheion (meaning "element") metron (meaning "measure"). Stoichiometry deals with calculations about the masses (sometimes volumes) of reactants and products involved in a chemical reaction. be prepared for lots of calculator use! Jeremias Benjaim Richter (1762-1807) was the first to lay down the principles of stoichiometry. In 1792 he wrote: " [Stoichiometry is the science of measuring the quantitative proportions or mass ratios in which chemical elements stand to one another.]

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4 STOICHIOMETRY is the part of chemistry that studies amounts of substances that are involved in reactions. You might be looking at the amounts of substances before the reaction. You might be looking at the amount of material that is produced by the reaction. Stoichiometry is all about amounts: Mass of Reactants (chemicals before the reaction) Mass of Products (chemicals after the reaction) Chemical Equations Molecular Weights of Reactants and Products Formulas of Various Compounds Why is Stoichiometry important? Synthesis of drugs and other complex molecules often requires multiple steps and a lot of chemicals. To minimize waste, we want to know exactly how much of the starting substance we need in order to make a known amount of product. Much like cooking in the kitchen. Also maximizing energy consumption requires specific mixtures of fuels…..
5 Na + + Cl - NaCl It takes one atom of sodium (Na) to combine with one atom of chlorine (Cl) to make the salt. Stoichiometry will tell you that if you have ten million atoms of sodium (Na) and only one atom of chlorine (Cl) you can only make one molecule of Sodium chloride (NaCl). 10,000,000 Na + + 1 Cl - NaCl + 9,999,999 Na + atoms atoms 2H 2 + O 2 2H 2 O one mole of a substance = mass of the atomic weight in grams, one mole of hydrogen (H) atoms = 1 g. One mole of oxygen (O) atoms = 16 g. you need 4 mole of H atoms and 2 moles of O atoms. That amount equals 4 g of H and 32 grams of O. Stoichiometry would show you that if you only had 8 g of O or H , all of the reactants would not be used. 4g of H 2 + 32g of O 2 36g of H 2 O or 8g of H 2 + 32g of O 2 36g of H 2 O + 4g of H 2

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6 The total mass, in grams, of reactants consumed is equal to the total mass, in grams, of product formed.
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lecture14%28chapt9%29 - Chapter 9 Stoichiometry The...

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