Ch.2 - Atoms & ElementsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
The Atom
Subatomic Particles
Atomic Mass
Periodic Table: Classifications
Periodic Table: Group Names
Periodic Table: Representative Elements & Transition Metals
Periodic Table: Element Symbols
Periodic Table: Elemental Forms
Periodic Table: Phases
Periodic Table: Charges
Calculating Molar Mass
Mole Concept
Law of Conservation of Mass
Law of Definite Proportions
Atomic Theory
Law of Multiple Proportions
Millikan Oil Drop Experiment
Rutherford Gold Foil Experiment
Additional Practice
Thomson's Cathode Ray Tube Experiment
The Chadwick Neutron Experiment
Mass Spectrometry
Additional Guides
Periodic table Charges (ignore)
Calculating Molar Mass (ignore)
Calculating Grams to Moles

"Different samples of a pure chemical compound always contain the same proportions of elements by mass."

Proust's Law of Definite Proportions

Concept #1: Law of Definite Proportions

Example #1: Two unknown compounds are examined. Compound A contains 2.0 grams of hydrogen and 32.0 grams of oxygen. Compound B contains 15.0 grams of hydrogen and 120.0 grams of oxygen. Do Compounds A and B represent the same compound?

Example #2: A compound contains only calcium and fluorine. A sample of the compound is determined to contain 2.00 g of calcium and 1.90 g of fluorine. According to the Law of Definite Proportions, how much calcium should another sample of this compound contain if it possesses 2.85 g of fluorine?

Practice: A 7.74 g sample of HCN is found to contain 0.287 g of H and 4.01 g N. Find the mass of carbon in a sample of HCN with a mass of 3.43 g.