1. Chapter 10: Stoichiometry
Notes_1
Today, will learn:
What is stoichiometry?
The Mole (concept)
Stoichiometry and moles
Writing and balancing chemical equation to determine stoichiometry
Chemistry _ Notes
Dr. Chirie Sumanasekera
1/23/ 2018

2. Particles, atoms, and molecules and chemical reactions
Ex: bread2 + cheese  grilled cheese sandwich
The bread and cheese in this example are elements and the sandwich is the molecule they form or product
Thinks of it this way: Each sandwich molecule is made up of a pair of bread slices ( diatomic molecule!!!) and one cheese atom
In chemistry, particles of a substance can be atoms or molecules.
If we take a Carbon-12 (C-12) element, for example, it is made up of a particles called at ATOMs.
But if we take a compound like carbon monoxide (CO) it is made up of particles called, MOLECULEs. Remember, that all molecules are made up of ATOMS.

3. Example: bread2 + cheese  grilled cheese sandwich Stoichiometry
1. What is Stoichiometry?
Stoichiometry is the relationship between the amount of reactants and the amount of products in a chemical reaction.
Example: bread2 + cheese  grilled cheese sandwich
Stoichiometry
Of this reaction:  1
Reactants
Product

4. 2. Mole:
Chemistry is a quantitative science - we need a "counting unit."
Number of particles in 1 mole = = 6.02 x1023
Avogadro’s Number = x 1023
Dozen = 12
The MOLE:
1 mole of any substance has the same number of PARTICLES as there in 12 grams of Carbon-12.
or,
1 mole of a substance contains the same number of particles as the Avogadro’s number (6.02 x 1023)

5. 3. Stoichiometry- relationships and moles
Stoichiometry is the relationship between the amount of reactants and the amount of products in a chemical reaction.
To determine the proportion of each substance in a reaction, we need to write balanced chemical equations first.
Example: bread cheese  grilled cheese sandwich
Product
Reactants
Stoichiometry
of this reaction: 
Number of moles: 1 mole mole  mole
bread Cheese grilled cheese sandwich
Molecules Atoms Molecules

6. 4. Writing chemical names and balancing chemical equations:
Substance 2C
2CO2
Moles of atoms
Moles of molecules
Subscript = number of atoms of an element (in a molecule)

7. Example:1

8. Particles, atoms, and molecules and chemical reactions
Ex_1: Lets make a grilled cheese sandwich (GCS) chemical reaction with Bread & Cheese:
Balanced equation:
bread2 + cheese  grilled cheese sandwich
The bread and cheese in this example are elements and the sandwich is the molecule or product formed by them in a chemical reaction!
Think of it this way:
Each sandwich molecule is made up of one Bread2 molecule and one cheese atom

9. Example:2

10. Particles, atoms, and molecules and chemical reactions
Balanced equation:
bread2 + cheese  grilled cheese sandwich
Ex_2: Lets make a molecule of Carbon dioxide!
Balanced equation:
O2 + C  CO2
Carbon atom
Carbon dioxide Molecule
Oxygen gas Molecule

11. Example:3

12. Stoichiometry of reactions
Ex_3: How many [product molecules are formed?
(a) Balanced equation:
__bread2 + __ cheese  __ grilled cheese sandwich
Molecules of GCS:
Left over Cheese:
Left over bread:
Limiting reactant: 10 10
__O2 + __C __CO2
(b)Balanced equation:
Molecules of CO2:
Left over C:
Left over O2 :
Limiting reactant:
Carbon atom
Carbon dioxide
Molecule
Oxygen gas Molecule 10 10

13. Stoichiometry of reactions
Ex_3: How many product molecules are formed?
(a) Balanced equation:
10 bread cheese  10 grilled cheese sandwich
Molecules of GCS: 10
Left over Cheese:0
Left over bread:0
Limiting reactant:0 10 10
(b)Balanced equation:
10 O C  10 CO2
Molecules of CO2: 10
Left over Cheese: 0
Left over bread:0
Limiting reactant:0
Carbon atom
Carbon dioxide
Molecule
Oxygen gas Molecule 10 10

14. Example:4

15. Stoichiometry of Limiting Reactions
Ex_3: How many [product molecules are formed?
(a) Balanced equation:
__bread2 + __ cheese  __ grilled cheese sandwich
Molecules of GCS:
Left over Cheese:
Left over bread:
Limiting reactant: 10 5
__O2 + __C __CO2
(b)Balanced equation:
Molecules of CO2:
Left over C:
Left over O2:
Limiting reactant:
Carbon atom
Carbon dioxide
Molecule
Oxygen gas Molecule 10 5

16. Stoichiometry of Limiting Reactions
Ex_4: How many product molecules are formed?
(a) Balanced equation:
5 bread cheese  5 grilled cheese sandwich
Molecules of GCS: 5
Left over Cheese:5
Left over bread:0
Limiting reactant: Bread 10 5
(b) Balanced equation:
5 O C  5 CO2
Molecules of CO2: 5
Left over C: 5
Left over O2 :0
Limiting reactant: O2
Carbon atom
Carbon dioxide
Molecule
Oxygen gas Molecule 10 5

17. Balancing chemical reactions to find the Stoichiometry of a reaction:
Write the balanced equation for burning (combustion) of carbon with Oxygen gas to form (a) one and (b) two moles of Carbon dioxide:
Steps:
Write the products and the reactants C + O2 -> CO2
Balance the equation so that there are equal numbers of each atom on either side
CO2
(a) _C + _O2
2CO2
(b) _C + _O2

18. Balancing chemical reactions to find the Stoichiometry of a reaction:
Write the balanced equation for burning (combustion) of carbon with Oxygen gas to form (a) one and (b) two moles of Carbon dioxide:
Steps:
Write the products and the reactants C + O2 -> CO2
Balance the equation so that there are equal numbers of each atom on either side
CO2
(a) 1C + 1O2
2CO2
(b) 2C + 2O2

19. Chapter 10: Stoichiometry
Today we learnt:
Stoichiometry is the ratios of reactants and products of a chemical reaction
1 mole of a substance contains 6.02 x1023 particles
Balanced equations tell us the number of moles of each substance in a chemical reaction
We learnt how to balance chemical reactions to figure out moles of reactants and products
Chemistry _ Notes
Dr. Chirie Sumanasekera
1/23/ 2018