Created by C. Ippolito June 2007 Chemical Quantities 10.1 The Mole: A Measurement of Matter 10.2 Mole-Mass and Mole-Volume Relationships 10.3 Percent Composition and Chemical Formulas 4/25/2019 Created by C. Ippolito June 2007 1

The Mole: A Measurement of Matter Objectives Describe methods of measuring the amount of something Define Avogadro’s number as it relates to a mole of a substance Distinguish between the atomic mass of an elements and its molar mass Describe how the mass of a mole of a compound is calculated 4/25/2019 Created by C. Ippolito June 2007 2

Created by C. Ippolito June 2007 Measuring Matter Three ways to measure amount: By Count use units that stand for a specific number of items dozen = 12 pair = 2 By Mass units that stand for the weight or mass kilogram pound By Volume use units that describe the space occupied quart liter 4/25/2019 Created by C. Ippolito June 2007 3

Created by C. Ippolito June 2007 What is a mole? Mole unit that measures a specific number of representative particles (atoms, molecules, formula units) 6.02 x 1023 – Avogadro’s number 4/25/2019 Created by C. Ippolito June 2007 4

Converting Particles to Moles 1 mole = 6.02 x 1023 particles 4/25/2019 Created by C. Ippolito June 2007 5

Converting Moles to Particles 1 mole = 6.02 x 1023 particles 4/25/2019 Created by C. Ippolito June 2007 6

The Mass of a Mole of an Element Molar Mass the atomic mass of an element expressed in grams is the mass of a mole of the element 4/25/2019 Created by C. Ippolito June 2007 7

The Mass of a Mole of a Compound To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound. 4/25/2019 Created by C. Ippolito June 2007 8

Mole-Mass and Mole-Volume Relationships Objectives Describe how to convert the mass of a substance to the number of moles of a substance, and moles to mass Identify the volume of a quantity of gas at STP 4/25/2019 Created by C. Ippolito June 2007 9

Mole-Mass Relationship Use the molar mass of an element to convert between the mass of a substance and the moles of a substance to convert moles to mass: to convert mass to moles: 4/25/2019 Created by C. Ippolito June 2007 10

Mole-Volume Relationship Avogadro’s Hypothesis equal volumes of gases at the same temperature and pressure contain equal number of particles Standard Temperature and Pressure (STP) 0°C (273K) and 1 atmosphere (101.3 kPa) At STP, 1 mole (6.02 x 1023 particles) of any gas occupies 22.4 L. Molar Volume space (22.4 L) occupied by 1 mole of ANY gas at STP 4/25/2019 Created by C. Ippolito June 2007 11

Calculating Volume at STP 4/25/2019 Created by C. Ippolito June 2007 12

Calculate Molar Mass from Density molar mass = density at STP x molar volume 4/25/2019 Created by C. Ippolito June 2007 13

Percent Composition and Chemical Formulas Objectives Describe how to calculate the percent by mass of an element in a compound Interpret an empirical formula Distinguish between empirical and molecular formulas 4/25/2019 Created by C. Ippolito June 2007 14

Percent Composition Compounds the relative amounts of elements in a compound Percent by Mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100% 4/25/2019 Created by C. Ippolito June 2007 15

Calculate % Comp from Mass Data 4/25/2019 Created by C. Ippolito June 2007 16

Calculate % Comp from Formula 4/25/2019 Created by C. Ippolito June 2007 17

Created by C. Ippolito June 2007 Empirical Formula Shows the smallest whole-number ratio of atoms in a compound 4/25/2019 Created by C. Ippolito June 2007 18

Empirical Formula (con’t) Shows the smallest whole-number ratio of atoms in a compound 4/25/2019 Created by C. Ippolito June 2007 19

Created by C. Ippolito June 2007 Molecular Formulas can be the same as the experimentally determined empirical formula or it is a simple whole-number multiple of the empirical formula it is the ratio of atoms in an ACTUAL molecule 4/25/2019 Created by C. Ippolito June 2007 20

Finding Molecular Formula 4/25/2019 Created by C. Ippolito June 2007 21