Chapter 9- Stoichiometry: The mass relationships between reactants and products in a chemical reaction. I have a yellow hat on! Stoichiometry is like following a recipe Focuses on mass or molar relationships Key is a balanced equation and reading the equation in terms of…Coefficients

Let’s try this: Na + Cl2 Type of reaction? Balanced equation How is this read in terms of moles? What are all the possible mole ratios? “RECIPE” for moles to moles, moles to mass, mass to moles and mass to mass

Let’s try this: Na + Cl2 NaCl Type of reaction? Balanced equation How is this read in terms of moles? What are all the possible mole ratios? “RECIPE” for moles to moles, moles to mass, mass to moles and mass to mass

Let’s try this: Na + Cl2 NaCl Type of reaction? Combination Balanced equation How is this read in terms of moles? What are all the possible mole ratios? “RECIPE” for moles to moles, moles to mass, mass to moles and mass to mass

Let’s try this: 2Na + Cl2 2NaCl Type of reaction? Combination Balanced equation How is this read in terms of moles? What are all the possible mole ratios? “RECIPE” for moles to moles, moles to mass, mass to moles and mass to mass

Let’s try this: 2Na + Cl2 2NaCl Type of reaction? Combination Balanced equation How is this read in terms of moles? 2 moles of Na react with 1 mole of Cl2 to produce 2 moles of NaCl

Let’s try this: 2Na + Cl2 2NaCl What are all the possible mole ratios? 2 mol Na 2 mol Na 1 mol Cl2 1 mol Cl2 2 mol NaCl 2 mol NaCl 2 mol NaCl 2 Mol NaCl 1 mol Cl2 2 mol Na 1 mol Cl2 2 mol Na

Let’s try this: 2Na + Cl2 2NaCl 5. “RECIPE” for moles to moles, moles to mass, mass to moles and mass to mass Remember that you cannot use a mass-mass ratio. You must convert to mol first and then back into grams.

Conversions of Quantities in Moles CO2 + 2LiOH → Li2CO3 + H2O How many moles of lithium hydroxide are required to react with 20 moles of carbon dioxide, the average amount exhaled by a person each day?

Conversions of Quantities in Moles CO2 + 2LiOH → Li2CO3 + H2O

Conversions of Quantities in Moles CO2 + 2LiOH → Li2CO3 + H2O 2 mol LiOH 1 mol CO2

Conversions of Quantities in Moles CO2 + 2LiOH → Li2CO3 + H2O 2 mol LiOH x mol LiOH 1 mol CO2 20 mol CO2 X

Conversions of Quantities in Moles CO2 + 2LiOH → Li2CO3 + H2O 2 mol LiOH x mol LiOH 1 mol CO2 20 mol CO2 x 40 mol LiOH X =

Let’s pretend we have 7,000,000 hot dogs Limiting Reagent Let’s pretend we have 7,000,000 hot dogs But only 600 hot dog buns X 1,000,000 X 100

Q- How many hot dogs can you make? Limiting Reagent Q- How many hot dogs can you make?

Q- How many hot dogs can you make? Limiting Reagent Q- How many hot dogs can you make? A – Only 600

Limiting Reagent Once a reactant is used up, there can be no more products produced (The substance that is used up first is called the) limiting reagent = the reactant that limits the amount of the other reactant that can be combined and thus the product that is produced Excess reagent = the substance not used up completely

Let’s try a problem: HCl + NaOH NaCl + H2O 2 mol 2.5 mol Determine the limiting reagent for this reaction. (This is done by comparing the 2 given value in a ratio.)

Pick one of the givens and solve: Let’s try a problem: HCl + NaOH NaCl + H2O 2 mol 2.5 mol Pick one of the givens and solve: 1 mol HCl x mol HCl 1 mol NaOH 2.5 mol NaOH x 2.5 mol HCl = =

Let’s try a problem: HCl + NaOH NaCl + H2O 2 mol 2.5 mol 2.5 mol HCl: But what does this mean? This means that in order to react ALL 2.5 mol NaOH, you would need AT LEAST 2.5 mol HCL. But you only have 2 mol HCl, so it LIMITS the reaction. Hence: limiting reagent.

Percentage Yield Theoretical yield = what you calculate or expect under perfect conditions Actual Yield = what you get in the lab Percentage Yield = x 100% Actual Yield Theoretical Yield