CHEMISTRY Matter and Change Chapter 10: The Mole

Table Of Contents Section 10.1 Measuring Matter CHAPTER10 Table Of Contents Section 10.1 Measuring Matter Section 10.2 Mass and the Mole Section 10.3 Moles of Compounds Section 10.4 Empirical and Molecular Formulas Section 10.5 Formulas of Hydrates Click a hyperlink to view the corresponding slides. Exit

SECTION10.1 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 Relate the mole to a common everyday counting unit. Convert between moles and number of representative particles. mole Avogadro’s number Chemists use the mole to count atoms, molecules, ions, and formula units.

Measuring Matter Counting Particles SECTION10.1 Measuring Matter Counting Particles Chemists need a convenient method for accurately counting the number of atoms, molecules, or formula units of a substance. The mole is * 1 mole is * , which is any kind of particle – an atom, a molecule, a formula unit, an electron, an ion, etc. The number is called Avogadro’s number.

Converting Between Moles and Particles SECTION10.1 Measuring Matter 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.) SECTION10.1 Measuring Matter Converting Between Moles and Particles (cont.) Particles to moles Use the inverse of Avogadro’s number as the conversion factor.

SECTION10.2 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 Convert between number of moles and the mass of an element. Convert between number of moles and number of atoms of an element. molar mass A mole always contains the same number of particles; however, moles of different substances have different masses.

Mass and the Mole The Mass of a Mole SECTION10.2 Mass and the Mole The Mass of a Mole 1 mol of copper (6.02 x 1023 atoms of copper) and 1 mol of carbon (6.02 x 1023 atoms of carbon) have different masses. One copper atom has a different mass than 1 carbon atom.

The Mass of a Mole (cont.) SECTION10.2 Mass and the Mole The Mass of a Mole (cont.) Molar mass is *. The molar mass of any element is numerically equivalent to its atomic mass and has the units g/mol.

Mass and the Mole Using Molar Mass Moles to mass SECTION10.2 Mass and the Mole Using Molar Mass Moles to mass 3.00 moles of copper has a mass of 191 g.

Using Molar Mass (cont.) SECTION10.2 Mass and the Mole Using Molar Mass (cont.) Convert mass to moles with the inverse molar mass conversion factor. Convert moles to atoms with Avogadro’s number as the conversion factor.

Using Molar Mass (cont.) SECTION10.2 Mass and the Mole Using Molar Mass (cont.) This figure shows the steps to complete conversions between mass and atoms.

SECTION10.3 Moles of Compounds Recognize the mole relationships shown by a chemical formula. 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. representative particle: an atom, molecule, formula unit, or ion

SECTION10.3 Moles of Compounds 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 SECTION10.3 Moles of Compounds 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 SECTION10.3 Moles of Compounds 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. The molar mass of a compound demonstrates the law of conservation of mass.

Converting Moles of a Compound to Mass SECTION10.3 Moles of Compounds Converting Moles of a Compound to Mass For elements, the conversion factor is the molar mass of the compound. The procedure is the same for compounds, except that you must first calculate the molar mass of the compound.

Converting the Mass of a Compound to Moles SECTION10.3 Moles of Compounds Converting the Mass of a Compound to Moles The conversion factor is the inverse of the molar mass of the compound.

Converting the Mass of a Compound to Number of Particles SECTION10.3 Moles of Compounds Converting the Mass of a Compound to Number of Particles Convert mass to moles of compound with the inverse of molar mass. Convert moles to particles with Avogadro’s number.

Converting the Mass of a Compound to Number of Particles (cont.) SECTION10.3 Moles of Compounds Converting the Mass of a Compound to Number of Particles (cont.) This figure summarizes the conversions between mass, moles, and particles.

Empirical and Molecular Formulas SECTION10.4 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 Determine the empirical and molecular formulas for a compound from mass percent and actual mass data. percent composition empirical formula molecular formula A molecular formula of a compound is a whole-number multiple of its empirical formula.

Empirical and Molecular Formulas SECTION10.4 Empirical and Molecular Formulas Percent Composition The percent 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.

Empirical and Molecular Formulas SECTION10.4 Empirical and Molecular Formulas Percent Composition (cont.) * is the percent composition of a compound. Percent composition of a compound can also be determined from its chemical formula.

Empirical and Molecular Formulas SECTION10.4 Empirical and Molecular Formulas Empirical Formula The empirical formula for a compound is *. You can calculate the empirical formula from percent by mass by assuming you have 100.00 g of the compound. Then, convert the mass of each element to moles. 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

Empirical and Molecular Formulas SECTION10.4 Empirical and Molecular Formulas Molecular Formula The molecular formula specifies *. Molecular formula is always a whole-number multiple of the empirical formula.

Empirical and Molecular Formulas SECTION10.4 Empirical and Molecular Formulas Molecular Formula (cont.)

SECTION10.5 Formulas of Hydrates Explain what a hydrate is and relate the name of the hydrate to its composition. crystal lattice: a three-dimensional geometric arrangement of particles Determine the formula of a hydrate from laboratory data. hydrate Hydrates are solid ionic compounds in which water molecules are trapped.

Formulas of Hydrates Naming Hydrates A hydrate is a * SECTION10.5 Formulas of Hydrates Naming Hydrates A hydrate is a * The number of water molecules associated with each formula unit of the compound is written following a dot. Sodium carbonate decahydrate = Na2CO3 • 10H2O

Naming Hydrates (cont.) SECTION10.5 Formulas of Hydrates Naming Hydrates (cont.)

Formulas of Hydrates Analyzing a Hydrate SECTION10.5 Formulas of Hydrates Analyzing a Hydrate When heated, water molecules are released from a hydrate leaving an anhydrous compound. To determine the formula of a hydrate, find the number of moles of water associated with 1 mole of hydrate.

Analyzing a Hydrate (cont.) SECTION10.5 Formulas of Hydrates Analyzing a Hydrate (cont.) Weigh hydrate. Heat to drive off the water. Weigh the anhydrous compound. Subtract and convert the difference to moles. The ratio of moles of water to moles of anhydrous compound is the coefficient for water in the hydrate.

Formulas of Hydrates Use of Hydrates SECTION10.5 Formulas of Hydrates Use of Hydrates Anhydrous forms of hydrates are often used to absorb water, particularly during shipment of electronic and optical equipment. In chemistry labs, anhydrous forms of hydrates are used to remove moisture from the air and keep other substances dry.

Measuring Matter Key Concepts SECTION10.1 Measuring Matter Study Guide Key Concepts The mole is a unit used to count particles of matter indirectly. One mole of a pure substance contains Avogadro’s number of particles. Representative particles include atoms, ions, molecules, formula units, electrons, and other similar particles. One mole of carbon-12 atoms has a mass of exactly 12 g. Conversion factors written from Avogadro’s relationship can be used to convert between moles and number of representative particles.

Mass and the Mole Key Concepts SECTION10.2 Mass and the Mole Study Guide Key Concepts The mass in grams of 1 mol of any pure substance is called its molar mass. The molar mass of an element is numerically equal to its atomic mass. The molar mass of any substance is the mass in grams of Avogadro’s number of representative particles of the substance. Molar mass is used to convert from moles to mass. The inverse of molar mass is used to convert from mass to moles.

Moles of Compounds Key Concepts SECTION10.3 Moles of Compounds Study Guide Key Concepts Subscripts in a chemical formula indicate how many moles of each element are present in 1 mol of the compound. The molar mass of a compound is calculated from the molar masses of all of the elements in the compound. Conversion factors based on a compound’s molar mass are used to convert between moles and mass of a compound.

Empirical and Molecular Formulas SECTION10.4 Empirical and Molecular Formulas Study Guide Key Concepts The percent by mass of an element in a compound gives the percentage of the compound’s total mass due to that element. The subscripts in an empirical formula give the smallest whole-number ratio of moles of elements in the compound. The molecular formula gives the actual number of atoms of each element in a molecule or formula unit of a substance. The molecular formula is a whole-number multiple of the empirical formula.