6.02 X 1023 Chemical Composition Adapted from www.chemistrygeek.com To play the movies and simulations included, view the presentation in Slide Show Mode. 6.02 X 1023 Adapted from www.chemistrygeek.com

The Mole A counting unit 6.02 X 1023 (in scientific notation) Dozen Ream Gross Mole 6.02 X 1023 (in scientific notation) 602,000,000,000,000,000,000,000 Avogadro’s Number Named in honor of Amedeo Avogadro (1776 – 1856) Equal volumes of any gas will have equal number of molecules

Just How Big is a Mole? Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

Learning Check Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects. 1. How many paper clips in 1 rapp? a) 1 b) 4 c) 8 2. How many oranges in 2.0 rapp? a) 4 b) 8 c) 16 3. How many rapps contain 40 gummy bears? a) 5 b) 10 c) 20

A Mole of Particles Contains 6.02 x 1023 particles = 6.02 x 1023 C atoms = 6.02 x 1023 H2O molecules = 6.02 x 1023 NaCl formula units (technically, ionics are compounds not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ions 1 mole C 1 mole H2O 1 mole NaCl

Avogadro’s Number as Conversion Factor 6.02 x 1023 particles 1 mole or 1 mole Note that a particle could be an atom, molecule or formula unit

Mole-Particle Conversions Convert 12 moles of Hydrogen to atoms - 12 moles x 6.02 x 1023 atoms = 7.22 x 1024 atoms 1 mole Convert 1.20 x 1024 molecules of Carbon Dioxide to moles 1.20 x 1024 molecules x 1 mole = 2 moles 6.02 x 1023 molecules The same conversion factor is used for all elements and compounds

Learning Check 1. Convert moles to particles a) 3.0 mole S b) 45 mole H2O c) 100 mole CaCO3 2. Convert particles to moles a) 500 Al atoms b) 1.87 x 1023 O2 molecules c) 3.01 x 1023 NaCl formula units

How do Mass and the Mole relate? Element Number of Atoms Mass of Sample (g) Hydrogen 6.02 x 1023 1.01 Carbon 12.01 Oxygen 16.00 Sodium 22.99 Aluminum 26.98 Iron 55.85 Even though the number of atoms does not change, the mass of all the atoms does change Note that the masses of the moles on the table above are the same as atomic mass on the periodic table (coincidence?) Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

Molar Mass The Mass of 1 mole (in grams) Equal to the numerical value of the element’s atomic mass (get from periodic table) 1 mole of C atoms = 12.01 g 1 mole of Mg atoms = 24.31 g 1 mole of Cu atoms = 63.55 g Also called Atomic Mass, Molecular Mass or Formula Mass Unit is always expressed as g/mol Round to hundredths place

Learning Check! State the Atomic Mass of each element A. Lithium B. Bromine C. Zinc D. Silver E. Mercury

Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 1 mole Ca x 40.08 g/mol + 2 moles Cl x 35.45 g/mol = 110.98 g/mol CaCl2 1 mole of N2O4

Learning Check! Find the Molar Masses of the following compounds A. H2O B. N2 C. Al(OH)3 D. C6H12O6 E. CaCO3

Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

Mole-Gram Conversion Factors Grams  Moles 1 mole molar mass Moles  Grams

Mole-Gram Conversions How many grams of Al are in 3.00 moles of Al? 3.00 mol Al x 26.98 g Al = 81.0 g of Al 1 mole Al How many moles of are in 3.00 g of Calcium? 3.00 g Ca x 1 mole Ca = 0.0749 40.08 g Ca mol Ca Molar Masses are taken from the Periodic Table

Learning Check! The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

Mole Road Map

Atoms/Molecules and Grams How many atoms of Cu are present in 35.4 g of Cu? 35.4 g Cu 1 mol Cu 6.02 X 1023 atoms Cu 63.55 g Cu 1 mol Cu = 3.4 X 1023 atoms Cu

Atoms/Molecules and Grams (WH) How many atoms of O are present in 78.1 g of O2? 78.1 g O2 1 mol O2 6.02 X 1023 molecules O2 2 atoms O 32.0 g O2 1 mol O2 1 molecule O2

Learning Check! How many atoms of K are present in 78.4 g of K?

Learning Check! What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)?

Percent Composition Percent Composition = Mass of the Element x 100% Mass of the Compound What is Percent Composition of Hydrogen in Water (H2O)? Hydrogen 1.01 x 2 = 2.02 Oxygen 16.00 x 1 = 16.00 18.02g % Hydrogen = 2.02 x 100% = 11.2% 18.02

Percent Composition What is the percent of carbon in C5H8NO4, a compound used to flavor foods and tenderize meats? a) 8.22 %C b) 24.3 %C c) 41.1 %C

Chemical Formulas of Compounds (WH) Formulas give the ratios of atoms or moles of each element in a compound Always a whole number ratio (the law of definite proportions). NO2 : 2 atoms of O for every 1 atom of N 1 mole of NO2 : 2 moles of O atoms to every 1 mole of N atoms If we know the relative number of moles of each element in a compound, we can determine a formula for the compound.

Types of Formulas (WH) Empirical Formula The formula of a compound that expresses the smallest whole number ratio of the atoms present. Molecular Formula The formula that states the actual number of each kind of atom found in one molecule of the compound. Molecular Formula Empirical Formula C6H12O6 CH2O C6H6 CH C4H6Cl2 C2H3Cl

Empirical Formula (WH) 1. Determine the mass in grams of each element present, if necessary. 2. Calculate the number of moles of each element. 3. Divide each by the smallest number of moles to obtain the simplest whole number ratio. If whole numbers are not obtained* in step 3), multiply through by the smallest number that will give all whole numbers * Be careful! Do not round off numbers prematurely

Divide all mole values by smallest (0.167) - A sample of a brown gas, a major air pollutant, is found to contain 2.34 g N and 5.34g O. Determine the empirical formula for this substance. N = 2.34g N x 1 mole = 0.167 moles of N 14.01 g O = 5.34 g O x 1 mole = 0.334 moles of O 16.00 g Divide all mole values by smallest (0.167) - N = 0.167 = 1 O = 0.334 = 2 0.167 0.167 Empirical Formula = NO2 (HONORS only)

Learning Check An oxide of Aluminum is formed by the reaction of 4.151 g of aluminum with 3.692 g of oxygen. Calculate the empirical formula

Empirical Formula from % Composition (WH) A substance has the following composition by mass: 60.80 % Na ; 28.60 % B ; 10.60 % H What is the empirical formula of the substance? Hint: Use sample size of 100 grams. This will contain 60.80 g of Na, 28.60 g of B and 10.60 g of H

Molecular Formula Find Empirical Formula Find Molar Mass of Empirical Formula Molar Mass of Compound will be given Divide Mass of Compound = n Mass of Emp. Formula Multiply subscripts in Emp. Formula by n to get Molecular Formula

Molecular Formula (WH) A compound has an empirical formula of NO2. The colourless liquid, used in rocket engines has a molar mass of 92.0 g/mole. What is the molecular formula of this substance? Mass of NO2 N = 1 x 14.01 = 14.01 O= 2 x 16.00 = 32.00 46.01 n = 92.00 g/mol = 2 46.01 g/mol Molecular Formula = N2O4

Learning Check A white powder is analyzed and found to have an empirical formula of P2O5. The compound has a molar mass of 283.88 g. What is the molecular formula?