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

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.

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 + 1  1 Reactants Product

2. Mole: Chemistry is a quantitative science - we need a "counting unit." Number of particles in 1 mole = 602213673600000000000000 = 6.02 x1023 Avogadro’s Number = 6.02 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)

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: bread2 + cheese  grilled cheese sandwich Product Reactants Stoichiometry of this reaction: 1 + 1  1 Number of moles: 1 mole + 1 mole  1 mole bread2 Cheese grilled cheese sandwich Molecules Atoms Molecules

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)

Example:1

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

Example:2

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

Example:3

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

Stoichiometry of reactions Ex_3: How many product molecules are formed? (a) Balanced equation: 10 bread2 + 10 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 O2 + 10 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

Example:4

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

Stoichiometry of Limiting Reactions Ex_4: How many product molecules are formed? (a) Balanced equation: 5 bread2 + 5 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 O2 + 5 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

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

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

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

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