Section 10.1 Measuring Matter

• Explain how a mole is used to indirectly count the number of particles of matter.

molecule: two or more atoms that covalently bond together to form a unit

mole

Avogadro’s number

• Relate the mole to a common everyday counting unit.

• Convert between moles and number of representative particles.

Chemists use the mole to count atoms, molecules, ions, and formula units.

Counting Particles

• Chemists need a convenient method for accurately counting the number of atoms, molecules, or formula units of a substance.

• The _______ is the SI base unit used to measure the amount of a substance.

• 1 mole is the amount of atoms in 12 g of pure carbon-12, or 6.02 1023 atoms.

• The number is called ___________________

Converting Between Moles and Particles

• Conversion factors must be used.

• Moles to particles

Number of molecules in 3.50 mol of sucrose

Converting Between Moles and Particles (cont.)

• Particles to moles

• Use the inverse of Avogadro’s number as the conversion factor.

Section 10.2 Mass and the Mole

• Relate the mass of an atom to the mass of a mole of atoms.

conversion factor: a ratio of equivalent values used to express the same quantity in different units

molar mass

• Convert between number of moles and the mass of an element.

• Convert between number of moles and number of atoms of an element.

A mole always contains the same number of particles; however, moles of different substances have different masses.

The Mass of a Mole

• 1 mol of copper and 1 mol of carbon have different masses.

•Because !!!!

• One copper atom has a different mass than 1 carbon atom.

So same number of atoms, but different masses. (ie 100 bricks or 100 feathers)

The Mass of a Mole (cont.)

• __________________ is the mass in grams of one mole of any pure substance.

• The molar mass of any element is numerically equivalent to its atomic mass and has the units g/mol.

Using Molar Mass

• Moles to mass

Using Molar Mass (cont.)

• Convert moles to mass by multiplying by the molar mass

• Convert mass to moles with the inverse molar mass conversion factor. (1 / molar mass)

• Convert moles to atoms with Avogadro’s number as the conversion factor.

• Convert atoms to moles with the inverse of Avagadro’s number (1 / Av. #)

MOLE MOUNTAIN

Section 10.3 Moles of Compounds

• Recognize the mole relationships shown by a chemical formula.

representative particle: an atom, molecule, formula unit, or ion

• Calculate the molar mass of a compound.

• Convert between the number of moles and mass of a compound.

• Apply conversion factors to determine the number of atoms or ions in a known mass of a compound.

Section 10.3 Moles of Compounds (cont.)

The molar mass of a compound can be calculated from its chemical formula and can be used to convert from mass to moles of that compound.

Chemical Formulas and the Mole

• Chemical formulas indicate the numbers and types of atoms contained in one unit of the compound.

• One mole of CCl2F2 contains one mole of C atoms, two moles of Cl atoms, and two moles of F atoms.

The Molar Mass of Compounds

• The molar mass of a compound equals

• the molar mass of each element, multiplied by the moles of that element in the chemical formula, added together.

• ie: mass of H2O = mass of 2 moles of H + mass of 1 mole of O.

• The molar mass of a compound demonstrates the law of conservation of mass.

Converting Moles of a Compound to Mass

• For elements, the conversion factor is the molar mass of the element.

• The procedure is the same for compounds, except that you must first calculate the molar mass of the compound.

Section 10.4 Empirical and Molecular Formulas

• Explain what is meant by the percent composition of a compound.

percent by mass: the ratio of the mass of each element to the total mass of the compound expressed as a percent

percent composition

empirical formula

molecular formula

• Determine the empirical and molecular formulas for a compound from mass percent and actual mass data.

A molecular formula of a compound is a whole-number multiple of its empirical formula.

Percent Composition

• The percent composition by mass of any element in a compound can be found by dividing the mass of the element by the mass of the compound and multiplying by 100.

Percent Composition (cont.)

• The percent by mass of each element in a compound is the ____________________ of a compound.

• Percent composition of a compound can also be determined from its chemical formula.

Empirical Formula

• The _____________________________ for a compound is the smallest whole-number mole ratio of the elements.

• The empirical formula may or may not be the same as the molecular formula.

Molecular formula of hydrogen peroxide = H2O2

Empirical formula of hydrogen peroxide = HO

Molecular Formula

• The _______________________ specifies the actual number of atoms of each element in one molecule or formula unit of the substance.

• Molecular formula is always a whole-number multiple of the empirical formula.