Introduction to Stoichiometry Part 1: Chemical Formulas

Matter: Stoichiometry

4 tasks you will learn to complete skillfully: 1. Determine # of Atoms in a Molecule

(Chemical Formula) 2. Determine Mass of a Molecule 3. Balance Chemical Equations 4. Convert from Mass to Moles and back

Stoichiometry is the quantitative relationship between the elements in a compound or between the compounds/elements in a chemical reaction.

Stoichiometry: Analogy You have been using stoichiometry your entire life! Consider a Basketball Team:

2 Guards (G) 2 Forwards (F)

1 Center (C)

Formula for one Team: CF2G2

Basketball Teams Two Teams: 2 CF2G2

4 Guards (G) 4 Forwards (F) 2 Centers (C) Formula for

One Team: CF2G2

Two Teams

10 Players!

+ +

How many Centers and Forwards are needed to have 6 basketball teams?

To build 6 teams, here is what we need: 6 Centers

CF2G2 Team formula is the key!

6 CF2G2

12 Forwards = 6 CF2G2 x 2 Forwards

1 CF2G2

1 CF2G2 =x 1 Center

New Imaginary Quantity:

tournament There are 8 of ANYTHING in a tournament

Example) An octopus has a tournament of legs

Using Formulas and Ratios

CF2G2 Formula for ONE team!

Basketball Teams How many forwards are in one tournament of basketball teams?

(Recall: there are 8 of ANYTHING in a tournament)

Example: Quidditch Team

1 Seeker (S) 3 Chasers (Ch)

1 Keeper (K)

Quidditch Team

7 Players!

+ +

(The concept of Quidditch is the property of J.K. Rowling)

What is the formula for a Quidditch Team?

2 Beaters (B)

Formula: B?Ch?K?S? 2 3 1 1 = B2Ch3KS

Example: Quidditch Team How many chasers are needed to build 107 quidditch teams?

To build 1 nitrous acid molecule, I need:

1 H atom 1 N atom 2 O atoms

Atoms H O N Molecule

structure

HNO2 formula

N O O H (nitrous acid)

Number of Atoms in a Molecule

To build 3 nitrous acid molecules, I need:

3 Molecules HNO2 formula

N O O H

(nitrous acid) N O O H N O O H

Stoichiometry

3 H atom, 3 N atoms, and 6 O atoms

8 of anything = 1 Tournament

To build 1 Tournament of nitrous acid molecules, I need: ? Tournaments of H ? Tournaments of N ? Tournaments of O

HNO2 formula

(My Imaginary Quantity) Recall

Introduction to Stoichiometry Part 1: Chemical Formulas

Credits Nitrous acid examples are adapted from Petrovich (with permission) Photo Credit: Duke Quidditch (http://www.facebook.com/dukequidditch/photos_stream)