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STOICHIOMETRY

STOICHIOMETRY. ---THE CALCULATIONS OF QUANTITIES IN CHEMISTRY AND CHEMICAL RX’S. CONSERVATIONS IN RX’S. ONLY #’S OF ATOMS AND MASS (g) ARE CONSERVED IN EVERY RX MOLES, VOLUME, AND MOLECULES ARE NOT NECESSARILY CONSERVED FROM REACTANTS TO PRODUCTS. CONSIDER A BALANCED EQUATION LIKE A RECIPE.

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STOICHIOMETRY

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  1. STOICHIOMETRY ---THE CALCULATIONS OF QUANTITIES IN CHEMISTRY AND CHEMICAL RX’S

  2. CONSERVATIONS IN RX’S • ONLY #’S OF ATOMS AND MASS (g) ARE CONSERVED IN EVERY RX • MOLES, VOLUME, AND MOLECULES ARE NOT NECESSARILY CONSERVED FROM REACTANTS TO PRODUCTS

  3. CONSIDER A BALANCED EQUATION LIKE A RECIPE • 1 EGG + 2 C. MILK + 3 C. FLOUR 1 CAKE “HOW MUCH” OF EACH INGREDIENT WOULD IT TAKE TO MAKE: 10 CAKES? 1000 CAKES? 1 MOLE OF CAKES?

  4. COMPLETE AND BALANCE • N2 + H2 NH3

  5. MOLE RATIOS • IN THE AMMONIA RX, THESE ARE THE 6 “MOLE RATIOS” THAT WE CAN USE FOR CONVERSION FACTORS • 1 MOL. N23 MOL. H21 MOL. N2 3 MOL. H2 1 MOL. N2 2 MOL. NH3 2 MOL. NH32 MOL. NH33 MOL. H2 1 MOL. N2 3 MOL. H2 2 MOL. NH3

  6. USE THE 2 MOLE FLOW CHARTS TO GET FROM MOLES OF ONE SUBSTANCE TO MOLES OF ANOTHER USING THESE MOLE RATIOS MOL MOL

  7. HOW MANY MOLES OF AMMONIA ARE PRODUCED WHEN .60 MOL. OF NITROGEN REACT WITH HYDROGEN? .60 MOL. N2 x 2 MOL. NH3 = 1.2 MOL NH3 1 1 MOL. N2

  8. How many moles of aluminum are needed to react with oxygen to produce 3.7 moles of aluminum oxide? • Write the balanced equation first!!!!! • Then multiply by the correct mole ratio!!!! • 3.7 mol. Al2O3 x 1

  9. MOLES TO MASS OR MASS TO MOLES • How many grams of nitrogen are required to react with 4.5 mol of hydrogen to produce ammonia (NH3)?

  10. 4.5 MOL. H2 X 1 MOL. N2 X 28.014 g N2 = 1 3 MOL. H2 1 MOL N2 42.021 g N2 42 g N2 ( 2 SIG FIGS)

  11. WE MAY NOW USE THE 2 FLOW CHARTS TO SOLVE FOR ANY OTHER QUANTITIES (LITERS, ATOMS, ETC.) ***REMEMBER ALL CALCULATIONS ARE BASED ON COMPLETE AND ACCURATE BALANCED EQUATIONS……................................................(OUR CHEMICAL RECIPES)

  12. LIMITING REAGENTS • WHEN ONE OF THE REACTANTS IS IN SHORT SUPPLY IT IS CALLED A “LIMITING REAGENT” • “EXCESS REAGENTS” ARE LEFTOVER REACTANTS

  13. Actual yield (AY)---the actual amount (usu. Grams) of a given product that is produced in a rx. • Theoretical yield (TY)---the amount of product (g) that should be produced from given amounts of reactants determined through stoichiometry calculations. • % yield----calculated by AY x 100 % TY

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