ALRIGHT DEEP BREATHS.

Imagine you are baking cookies. The recipe says: 2 cups flour + 1 cup sugar = 12 cookies. If you want 24 cookies, you simply double everything.

That is stoichiometry, chemistry’s recipe math. It tells us how much reactant we need and how much product we will get. In this lesson, we will break it down step by step using the mole, Avogadro’s number, and balanced equations.

What Is Stoichiometry?

Stoichiometry is the part of chemistry that deals with quantities in reactions. It answers two main questions:

• How much reactant is needed to make a certain amount of product
• How much product can be made from a certain amount of reactant

Stoichiometry is built on three ideas:

1. Balanced chemical equations
2. The mole concept
3. Unit conversions

The Mole: Chemistry’s Counting Unit

A mole (mol) is a counting unit chemists use for atoms and molecules, since they are far too small to count individually.

Avogadro’s Number:

1 mol = 6.022 × 10²³

Examples:

• 1 mol of carbon contains 6.022 × 10²³ carbon atoms
• 1 mol of water contains 6.022 × 10²³ water molecules

Analogy: A mole is to atoms what a dozen is to eggs. It is simply a shortcut for very large numbers.

Molar Mass

The molar mass is the mass of one mole of a substance, measured in grams per mole. You calculate it using the periodic table by adding the atomic masses of all the atoms in a compound.

Example:

H₂O → 2(1.01) + 16.00 = 18.02 g/mol

Common Conversions in Stoichiometry

You Have	You Want	What to Do
Mass (g)	Moles	Divide by molar mass
Moles	Particles	Multiply by Avogadro’s number
Moles of A	Moles of B	Use mole ratio from balanced equation
Moles	Mass (g)	Multiply by molar mass

Mole Ratios

Balanced chemical equations tell us the ratio of reactants to products.

Example:

2H_2 + O_2 \rightarrow 2H_2O

From the equation:

• 2 mol H₂ reacts with 1 mol O₂
• Produces 2 mol H₂O

These ratios become conversion factors in stoichiometry problems.

Sample Problems 🙂

Recap Chart

Concept	Description
Mole	6.022 × 10²³ particles
Molar Mass	Mass of 1 mol of a substance (from periodic table)
Balanced Equation	Provides mole ratios of reactants and products
Mole Ratio	Conversion factor between substances
Stoichiometry	The math of predicting amounts in a chemical reaction

Pro Tip

Always start with what you are given, convert it to moles, use the mole ratio to connect reactants and products, and then convert to the unit you need (grams, liters, or particles).

Thought to Take With You

I don’t have any thoughts here guys. We can do this though, trust me.