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**Mole Ratios Limiting Reagent % Yield Gas Stoichiometry**

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Stoichiometry Chemistry is often called the science of proportions; Kitchen Chemistry/Recipes Stoichiometry : the study of chemical quantities based on a balanced equation.

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Stoichiometry Measureable and Quantitative relationship between reactants and products So, a chemical reaction takes place: Identify: Classification: Law of Conservation of Mass:

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You Must Remember: To BALANCE every equation

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Remember the mole?? Quantities in chemical equations are counted as moles.

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Chemical Ratios Substances in a balanced equation are always in a given proportion to each other. 1N2 + 3H2 2NH3 The proportions can be written as ratios.

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**Mole Ratios These proportions are called “mole ratios”.**

1N2 + 3H2 2NH3 For Every There are/is Creating ratio 1N2 3H2 1mol N2/3mol H2 2NH3 N2

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Mole Ratios What is the mole ratio found in the balanced equation below? N2O5 NO2 + O2

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The “Given” If 2 moles of N2O5 is reacted, how many moles of NO2 will be formed? There is always a given in a stoichiometry problem that includes A numeric value (2) A metric unit (moles) A substance (N2O5)

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**Mole-Mole Calculation**

If 2 moles of N2O5 is reacted, how many moles of NO2 will be formed? 1) 2 mol N2O5 x mole ratio (which one?) 2) 2 mol N2O5 x mol N2O5 (cancel the given) 3) 2 mol N2O5 x mol NO2 (write what you want) mol N2O5

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**Mole-Mole Calculation**

1- Balance the equation 2- Write down your given 3- Use conversion factors to convert moles (use the coefficients here) We call this the Heart of the equation

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**Heart of Every Equation**

mol unknown = mol given

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**Mole-Mole Calculations**

Coef mol _______________________ mol given coef mol unknown coef mol given

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**Mole-Mass Problem mol A 1 mol B**

How much (mass) B can be formed from a given number of moles of A? mol A x mol B x g B = g B mol A mol B 1) The mol-mol ratio comes from the equation 2) The mol-mass ratio comes from the periodic table

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C3H8 + 5O2 3CO2 + 4H2O 5.4 moles of propane (C3H8) is converted into how many moles of carbon dioxide?

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**Mole-Mass Calculations**

____________________________________ Molar mass (g) mol given coef mol unknown coef mol given 1 mol

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4NH3 + 5O2 6H2O + 4NO How many grams of H2O are produced if 1.9 mol of NH3 are combined with excess oxygen?

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Mass-Mole Problem How many moles of B can be formed from a given mass of A? g A x 1 mol A x mol B x = mol B g A mol A 1) The mol-mol ratio comes from the equation 2) The mol-mass ratio comes from the periodic table

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**Mass-Mole Calculations:**

mol given mol coef mol unknown __________________________________ molar mass coef mol given (g)

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Fe2O3 + 3CO -> 2Fe + 3CO2 How many grams of carbon dioxide are produced with 2 moles of iron (3) oxide?

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Mass-Mass Problem How much (mass) B can be formed from a given mass of A? g A x 1 mol A x mol B x g B = g B g A mol A mol B 1) The mol-mol ratio comes from the equation 2) The mol-mass ratio comes from the periodic table

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**Mass-Mass Calculations:**

g-given mol coef mol molar mass unknown (g) ____________________________________ molar mass coef mol mol given

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Fe2O3 + 3CO -> 2Fe + 3CO2 How many grams of iron would be produced using 25 grams of iron (3) oxide?

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**Mole Ratios Limiting Reagent-LR % Yield Gas Stoichiometry**

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Limiting Reagent Limiting reagent = a reactant that limits the amount of product that can be made It can also be thought of as a limiting ingredient

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**Limiting Reagent Recipe: peanut butter and jelly sandwich**

2Br + 3Pb + 2Je 1 Sa 3 ingredients necessary to produce one sandwich Could any one of these run out before the other two?

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**Excess Reagents Excess = there’s extra of this substance**

*the substance won’t run out *don’t include this reagent in the calculation If you have 20 loaves of bread, 1 jar of peanut butter and 1 jar of jelly – which ingredient is in excess?

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Limiting Reagent To determine the limiting reagent, more than one problem must be done Ex: You have 8 slices of bread and 9 T of peanut butter. Which is the limiting ingredient? (2Br + 3Pb + 2Je 1 Sa) 8 Br x 1Sa = 4 Sa 9 Pb x 1Sa = 3 Sa 2 Br Pb

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Limiting Reagent The reactant that produces the smallest amount of product is the limiting reagent. 8 Br x 1Sa = 4 Sa 9 Pb x 1Sa = 3 Sa 2 Br Pb Limiting reagent Smaller quantity

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**Uses for Limiting Reactants**

Nutritional value of food for body Concentration of pollutants

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**What to do (write these down):**

Balance equation Convert: 1-have to moles 2-need to moles Compare have : need One must be > or < ID the LR Excess compare your have : need

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**Cu + AgNO3 Cu(NO3)2 + Ag Balance first**

Know: you have 3.5 grams of Cu and 6 grams of AgNO3. What is the LR and what is excess?

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Cu + AgNO3 Cu(NO3)2 + Ag 3.5 grams of Cu / 6 grams of AgNO3

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Al + O2 Al2O3 Balance Known: mole of powdered Al is placed in a container with moles of oxygen. What is the limiting reactant?

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Al + O2 Al2O3 0.048 mole Al / moles of oxygen

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**Stoichiometry Ratios and Proportions Mole Ratios Limiting Reagent**

Yield Gas Stoichiometry

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**% Yield Theoretical Yield = calculated mass of product**

Actual Yield = mass of product found in lab Percent Yield = actual yield x 100% theoretical yield

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Percent Yield Methanol can be produced through the reaction of CO and H2 in the presence of a catalyst. CO(g) + 2H2(g) CH3OH(l) If 75.0 g of CO reacts to produce 68.4 g CH3OH, what is the percent yield of CH3OH? 79.8%

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% Yield Chlorobenzene, C6H5Cl is used in the production of many important chemicals, such as aspirin, dyes, and disinfectants. C6H6(l) + Cl2(g) C6H5Cl(s) + HCl(g) When 36.8 g of C6H6 react with an excess of Cl2, the actual yield of C6H5Cl is 38.8 g. What is the percent yield of C6H5Cl? 73.2%

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% Yield Aluminum reacts with excess copper (II) sulfate according to the reaction below. If 1.85 g of Al react and the percent yield of Cu is 56.6%, what mass of Cu is produced? Al(s) + CuSO4(aq) Al2(SO4)3(aq) + Cu(s) 3.70 g

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**Stoichiometry Ratios and Proportions Mole Ratios Limiting Reagent**

Yield Gas Stoichiometry

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***This volume assumes standard temperature and pressure conditions**

Molar Volume Molar volume = the space that one mole of ANY gas fills 1 mole = *22.4 liters Remember: 1 L = 1000 mL *This volume assumes standard temperature and pressure conditions

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Molar Volume 1) A quantity of gas has a volume of cm3. How many moles of gas are there?

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**Molar Volume 2) Hydrogen sulfide occupies 278.2cm3. **

What is the mass of the hydrogen sulfide?

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Gas Stoichiometry Instead of counting moles in a reaction, we can also count liters of a gas. 1 liter of N2 reacts with 3 liters of H2 to produce 2 liters of NH3

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Gas Stoichiometry What volume of water vapor will be formed when 8.2 L of H2 reacts with excess O2? 2H2 (g) + O2 (g) 2H2O(g) Use a liter-liter ratio!

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Gas Stoichiometry What volume of ammonia will form when 52.5 g of nitrogen reacts with excess hydrogen? gN2 mol N2 mol NH3 L NH3 gN2 mol N2 L N2 L NH3

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**Keep digging! No pun intended**

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