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Stoichiometry Limiting Reactants

Stoichiometry Limiting Reactants. Stoichiometry. Stoichiometry enables us to compare amounts of two substances in a balanced chemical reaction. Simple Example. If you have 6 slices of bread, how many ham sandwiches could you make? 2 Bread + 1 Ham → 1 Sandwich. 6. 2. 1. 3.

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Stoichiometry Limiting Reactants

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  1. StoichiometryLimiting Reactants

  2. Stoichiometry Stoichiometry enables us to compare amounts of two substances in a balanced chemical reaction.

  3. Simple Example If you have 6 slices of bread, how many ham sandwiches could you make? 2 Bread + 1 Ham → 1 Sandwich 6 2 1 3

  4. Mole Ratios A mole ratio is a whole number relationship between two substances in a balanced chemical equation.

  5. Converting Substances 2Na(s) + Cl2(g) → 2 NaCl(s) How many moles of salt could be made if you had 5.00 moles of chlorine gas? ANALYZE (have/need, conv. factor) PLAN (setup dimensional analysis) 5.00 mol Cl2 2 mol NaCl 10 mol NaCl 1 mol Cl2 EVALUATE (crunch numbers)

  6. Converting Mass to Mass 2H2(g) + O2(g) → 2H2O(l) How many grams of water could be made if you had 75.0 grams of oxygen? ANALYZE (have/need, conv. factors) g O2 mol O2  mol H2O  g H2O PLAN (setup dimensional analysis) 18.02 g H2O 84.5 g H2O 2 mol H2O 1 mol O2 75.0 g O2 32.00 g O2 1 mol H2O 1 mol O2 EVALUATE (crunch numbers)

  7. Limiting Reactants The first species that runs out in a reaction prevents the reaction from continuing. It is the limiting reactant. 1 body + 4 tires → 1 car

  8. Excess Reactants The species that are left over from the beginning are excess reactants. 1 body + 4 tires → 1 car 8 bodies 4 tires 32 tires 1 body 48 tires – 32 tires = 16 excess tires

  9. Percentage Yield We use percentage yield to determine how efficient a chemical reaction is. x 100 This can be done with grams or moles. Reactions cannot exceed 100% yield.

  10. Percentage Yield Example If 152 grams of CO2 are produced in a reaction, but the theoretical yield was calculated to be 175 grams of CO2, what is the percentage yield?

  11. Percentage Yield Practice Find the percentage yield if 5.50 moles of NaCl are produced from the reaction of 6.00 moles of sodium with excess chlorine gas. __Na + __Cl2 → __NaCl

  12. Percent Composition The percent composition of a substance indicates what percent of each atom is present in the compound (by mass). x 100 The sum of the percent compositions must be 100%

  13. Percent Composition Example Find the percent composition of carbon in a sample of CO2.

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