# Chapter 9 Stoichiometry.

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Chapter 9 Stoichiometry

9.1 & 9.2 Ideal Stoichiometric Calculations
Stoichiometry - the study of the quantitative measurement problems between chemical formulas, reactions and equations.

Atoms, molecules, particles
The Mole Map Liters Atoms, molecules, particles Grams Mole 22.4 L 6.022 x1023 Molar Mass

Stoichiometric Conversions
Quick Review using the mole map Ex1: 0.15 mol NaOH convert to grams Ex2: 9.00g MgCl2 convert to atoms of Chlorine

Stoichiometric Conversions
Reaction stoichiometry Example - combustion of propane: C3H8 + __O2  __CO2 + __H2O Thus, for every 1 propane, 5 moles of diatomic oxygen are required to produce 3 moles of carbon dioxide and 4 moles of water.

The New Mole Map Mole Grams Liters Molecules Coefficients Molecules

Stoichiometric Conversions
Four Core Steps: Step #1 Write a BALANCED equation Step #2 Go to moles Step #3 Mole to Mole - cross the bridge Step #4 Go to the desired unit

Stoichiometric Conversions
Ex1: How many moles of water vapor are created from 2 moles of Hydrogen? Balanced equation Go to Mole Mole to Mole Desired Unit

Stoichiometric Conversions
Ex2: How many grams of water vapor are created from 64.0 grams of Oxygen? Balanced equation 2H2(g) + O2(g)  2H2O(g) Go to Mole Mole to Mole Desired Unit

Stoichiometric Conversions
Ex3: How many liters of H2O (g) are made from 5.00 L of Oxygen? Balanced equation 2H2(g) + O2(g)  2H2O(g) Go to Mole Mole to Mole Desired Unit

Stoichiometric Conversions
Ex4: How many Liters of Oxygen are needed to react with g C5H12? Balanced equation Go to Mole Mole to Mole Desired Unit

Stoichiometric Conversions
Ex5: How many grams of solid lithium hydroxide are needed to react with 8.50 grams of carbon dioxide gas? (Lithium hydroxide + carbon dioxide yields Lithium carbonate and water) 9.23g LiOH

Stoichiometric Conversions
Ex6: How many grams of water are produced from 2.00 moles of carbon dioxide and excess amount of lithium hydroxide? 36.0g Ex7: How many moles of lithium carbonate are produced from 152 grams of carbon dioxide and an excess amount of lithium hydroxide? 3.45mol

9.3 Limiting Reactant Problems and % Yield...
The Limiting Reactant causes the reaction to stop…it is the reactant that is all used up in the chemical reaction.

Limiting Reactant Ex1: How many grams of Magnesium Chloride can be made from 3.64 g of magnesium and 7.10 g of Chlorine gas? a: How much of the excess reactant did you use? b: What percent of the excess was unused? ……

Limiting Reactant How many grams of Magnesium Chloride can be made from 3.64 g of magnesium and 7.10 g of Chlorine gas?

Limiting Reactant How much of the excess reactant did you use?

Limiting Reactant What percent of the excess was unused?

Limiting Reactant and % Yield
.From the equation: 2 HCl + Zn  ZnCl2 + H2 How many liters of H2 can be made starting with 20.0 grams of Zn and 25.5 g HCl? How many grams of Zinc chloride will be made? Identify the limiting and excess reactants. How much of the excess reactant is needed? How much of the excess reactant is left over?

Limiting Reactant 2 HCl + Zn  ZnCl2 + H2
How many liters of H2 can be made starting with 20.0 grams of Zn and 25.5 g HCl?

Limiting Reactant 2 HCl + Zn  ZnCl2 + H2
How many grams of Zinc chloride will be made?

Limiting Reactant 2 HCl + Zn  ZnCl2 + H2

Limiting Reactant Identify the limiting and excess reactants.
How much of the excess reactant is needed? How much of the excess reactant is left over?

% Yield % yield = mass produced x 100 mass theoretically produced

% Yield Ex1: If combusting 9.62 g of SO2 produces g of SO3, calculate the % yield.

So, if the % yield is ________, then the actual yield is:
Ex2: Reacting 4.20 grams of Nitrogen with g of Hydrogen produces ?g of NH3 if there is a 75.5 % yield? Thus, the limiting reactant, H2, theoretically produces _________ grams of NH3. So, if the % yield is ________, then the actual yield is: