Chemistry Honors Willson - Chapter 8 and 9 Test

Mole

6.022×10²³ particles; counting unit for atoms/molecules/ions

Avogadro's Number

6.022×10²³

Atoms → Moles Conversion

Atoms ÷ 6.022×10²³ = moles

Moles → Atoms Conversion

Moles × 6.022×10²³ = atoms

Grams → Moles

Grams ÷ molar mass (g/mol)

Moles → Grams

Moles × molar mass (g/mol)

Conversion Backbone

Atoms ⇄ Moles ⇄ Grams (via Avogadro’s # and molar mass)

Molar Mass

Mass of 1 mole of a substance (g/mol)

Percent Composition

(Mass of element ÷ molar mass) × 100

Empirical Formula

Simplest whole-number ratio of atoms in a compound

Steps to Find Empirical Formula

% → grams → moles → divide by smallest → whole numbers

Molecular Formula

Actual atom ratio; whole-number multiple of empirical formula

Steps to Find Molecular Formula

Molar mass ÷ empirical mass = multiplier → multiply subscripts

Hydrate

Compound with water molecules attached (ex. CuSO₄·5H₂O)

Finding Formula of a Hydrate

Heat to remove water → find moles salt & water → divide to get ratio

Chemical Reaction

Process where reactants form new products

Reactants

Starting substances

Products

Substances produced

Coefficient

Large number in front of formula; indicates # of molecules

Subscript

Small number; indicates # of atoms in a molecule

Symbols in Equations

+, →, (s), (l), (g), (aq)

Law of Conservation of Mass

Matter isn't created/destroyed → equations must be balanced

Balancing Equations Steps

Write formula → count atoms → change coefficients → recheck

Word Equation → Chemical Equation

Translate words → write formulas → balance

Synthesis Reaction

A + B → AB

Decomposition Reaction

AB → A + B

Single Replacement Reaction

A + BC → AC + B

Double Replacement Reaction

AB + CD → AD + CB

Combustion Reaction

Hydrocarbon + O₂ → CO₂ + H₂O

Predicting Products

Identify reaction type + form correct ionic compounds

Diatomic Seven

Br₂, I₂, N₂, Cl₂, H₂, O₂, F₂

When to Write Diatomic Elements

When they are alone/uncombined in a reaction

Importance of Polyatomic Ions

Needed to write correct formulas and predict products