Chapter 9

Stoichiometry

9.1 & 9.2 Ideal Stoichiometric Calculations

Stoichiometry - the study of the quantitative measurement problems between chemical formulas, reactions and equations.

The Mole Map

Liters

Atoms, molecules, particles

Grams

Mole

22.4 L

6.022 x10 23Molar Mass

Stoichiometric Conversions

Quick Review using the mole mapEx1:

0.15 mol NaOH convert to grams

Ex2: 9.00g MgCl2 convert to atoms of Chlorine

Stoichiometric Conversions

Reaction stoichiometryExample - 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 NewNew Mole Map

Mole Mole

GramsGrams

Liters 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 14.40 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 11.95 g of SO3, calculate the % yield.

% Yield

Ex2: Reacting 4.20 grams of Nitrogen with 0.800 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: