Some Basic Concepts in Chemistry Cheatsheet

Cheat Codes & Shortcuts

• Mole: SI unit for amount of substance; contains \(6.022 \times 10^{23}\) particles (Avogadro's number).
• Molar Mass: Mass of one mole in grams; \( \text{M} = \frac{\text{mass}}{\text{moles}} \).
• Empirical Formula: Simplest whole-number ratio of atoms.
• Molecular Formula: Actual number of atoms of each element in a molecule.
• Stoichiometry: Use balanced equations to relate moles, mass, & volume.
• Limiting Reagent: Reactant that runs out first, limits product formed.
• Atomic Mass Unit (amu): \(1\,\text{amu} = 1/12\) mass of a carbon-12 atom.
• Law of Conservation of Mass: Mass is neither created nor destroyed in chemical reactions.
• Percentage Composition: \( \% = \frac{\text{mass of element}}{\text{total mass}} \times 100 \).
• Avogadro's Law: Equal volumes of gases at same T and P contain equal number of molecules.

Quick Reference Table

Advice

Chemistry Quick Tips

• Converting grams → moles: \( \text{n} = \frac{\text{mass}}{\text{molar mass}} \).
• Empirical formula steps: Convert mass to moles, divide by smallest, round to nearest whole number.
• Mole concept: Use Avogadro’s number whenever particles are asked.
• Volume of gas at STP: \(1\,\text{mol} = 22.4\,\text{L}\) (for ideal gases at STP).
• Limiting reagent: Compare mole ratios from balanced equation.