Limiting Reactants Chemistry Unit 4.5, Day 3

M&M Opening Element Do NOT eat any M&M’s yet Make as many of the following groups: 1 Red 2 Blue 3 Green 2 Yellow How many groups did you make? Which of the above colors did you run out of first? Which colors do you have left over? How does this relate to Chemistry?

Relating M&M’s to Chemistry Think of each color M&M as a reactant Think of the final group as the product Why did you stop making “products” In other words, why did you stop making new groups?

Why Do Reactions Stop? Limiting Reactants: Excess Reactants: The reactant which limits the extent of the reaction, and therefore determines the amount of product produced Excess Reactants: The left-over reactants

Illustrating the Chemical Concept 3N2 + 3H2  2NH3 + 2N2 Interested in finding the amount of NH3 Break down each compound into atoms 6N + 6H  2N + 6H Which element has atoms left over? Excess Reactant Which element was completely used up? Limiting Reactant

Determining the Limiting Reactant S8 + 4Cl2  4S2Cl2 Rxn: 200g Sulfur reacts with 100g Chlorine NOTE: Mass of S8 = 256g/mol; Mass of Cl2 = 70g/mol Determine the number of moles of each reactant

Determining the Limiting Reactant Determine if the reactants are in the correct mole ratio as given by the balanced equation Equation’s Mole Ratio: Actual Mole Ratio: 4 mol Cl2 1 mol S8

Determining the Limiting Reactant Identify the reactant which does not match it’s required amount Limiting Reactant: ____ Excess Reactant: ____

Determining Amount of Product Even though you are given both amounts of reactants, you can ONLY use the Limiting Reactant’s amount to calculate the product’s mass:

Determining Amount of Product Helpful Information: Mass of Cl2 = 70g/mol Mass of S2Cl2 = 135g/mol

Checks for Understanding P4 + 5O2  P4O10 Which is the Limiting Reactant? Which is the Excess Reactant? Determine the amount of P4O10 produced when 25g of P4 reacts with 50g of O2. Helpful Information: P4 Molar Mass = 124 g/mol O2 Molar Mass = 32 g/mol P4O10 Molar Mass = 284 g/mol

Guided Practice: Think-Pair-Share For each of the following reactions: Determine the Limiting Reactant Determine the Excess Reactant Determine the amount of Product 6Na + Fe2O3  3Na2O + 2Fe 100g Na reacts with 100g Fe2O3, determine the amount of Fe produced Na Molar Mass = 23g/mol Fe2O3 Molar Mass = 160g/mol Fe Molar Mass = 56g/mol

Guided Practice: Think-Pair-Share For each of the following reactions: Determine the Limiting Reactant Determine the Excess Reactant Determine the amount of Product 2. 6CO2 + 6H2O  C6H12O6 + 6O2 88g CO2 reacts with 64g H2O, determine the amount of C6H12O6 produced CO2 Molar Mass = 44g/mol H2O Molar Mass = 18g/mol C6H12O6 Molar Mass = 180g/mol

Guided Practice: Think-Pair-Share For each of the following reactions: Determine the Limiting Reactant Determine the Excess Reactant Determine the amount of Product 3. 8P4 + 3S8  8P4S3 100g P4 reacts with 100g S8, determine the amount of P4S3 produced P4 Molar Mass = 124g/mol S8 Molar Mass = 256g/mol P4S3 Molar Mass = 220g/mol

Guided Practice: Think-Pair-Share For each of the following reactions: Determine the Limiting Reactant Determine the Excess Reactant Determine the amount of Product 4. Cl2 + C6H6  C6H5Cl + HCl 45g Cl2 reacts with 45g C6H6, determine the amount of C6H5Cl produced Cl2 Molar Mass = 70g/mol C6H6 Molar Mass = 78g/mol C6H5Cl Molar Mass = 112g/mol

Guided Practice: Think-Pair-Share For each of the following reactions: Determine the Limiting Reactant Determine the Excess Reactant Determine the amount of Product 5. Ni + 2HCl  NiCl2 + H2 5g Ni reacts with 25g HCl, determine the amount of NiCl2 produced Ni Molar Mass = 59g/mol HCl Molar Mass = 35g/mol NiCl2 Molar Mass = 129g/mol

Independent Practice: Complete the following questions Work quietly with your partner This worksheet is due NEXT class Raise your hand if you have questions!