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.