Chem 11 - Moles

What is the Mole (3)

• 1 dozen = 12 (Ex. 1 dozen of calculators = 12 calculators)

• 1 mole = 6.022 ×10²³ (Ex. 1 mol of books = 6.022 ×10²³ books)

  • Purpose: Represent a quantity of atoms or particles (Easier to write 1 mole than 6×10²³ atoms)

Relative mass (4)

• The mass of one thing in terms of another

  • Usually relative/compared to the smallest thing

• Calculation: Object Mass/Smallest Object Mass

• Dalton assumed H was the lightest → Mass = 1 (All elements are relative to H)

Law of conservation of mass (3)

• Lavoisier, 1789

• Matter cannot be created or destroyed in a chemical reaction

• Means we can balance equations

Law of definite proportions (2)

• Proust, 1789

• A chemical compound always contains the same proportions of elements by mass

Law of multiple proportions (2)

• Dalton, 1808

• If 2 elements form 1+ compound between them, then the ratios of the masses of the 2 elements will be small whole numbers

Atomic mass (amu) (2)

• The mass of one atom of a particular element (relative to the mass of H)

• Found on the periodic table

Formula mass (3)

• Elements are measured relative to carbon (12.000 amu)

  • Carbon = cheaper, more abundant, easy to weigh

• Calculation: Find # of atoms, multiply by the amu, total up

Molar mass (2)

• Mass in grams of 1 mole of the particles that make up the substance

  • Equal to the formula mass (amu) w/ units change to grams

• Ex. Fe = 55.8 g/mol