Warm-up: Intro activity Determine, to the greatest precision and accuracy possible, the thickness of a piece computer paper? Determine which of the following has the most amount of pieces (not necessarily worth the most money). Do you need any more information? 1 kg of pennies 1 kg of nickels 1 kg of dimes Brainstorm as many words as you can that are directly related to numbers (for example, 1 dozen=12)

coefficients give ratios coefficients of a balanced equation give the ratio of molecules in the reaction 2H2 (g) + O2 (g)  2 H2O (l) ___ molecules of hydrogen gas react with ___ molecules of oxygen gas to give ___ molecules of water

Correct Ratio of molecules 2H2 : 1O2 : ?H2O 2 hydrogen molecules 1 oxygen molecule 2 water molecules

? Wrong Ratio of molecules 1H2 : 1O2 : ?H2O 1 hydrogen molecule 1 oxygen molecule ?

Problems in chemistry… Atoms are too small to talk about and measure easily Atoms of different elements have different masses (periodic table)

Also… Can you “measure out” 2 molecules of hydrogen and 1 molecule of water??? Why or why not??? What do unit do we use to measure? How many molecules are in one gram?

Since one gram contains a huge amount of molecules or atoms... chemists have devised a special counting unit to understand the large numbers of molecules or atoms measured in the lab. This unit is called the mole!

What is a “counting unit”? Bakers use the counting unit “dozen” to understand they have 12 donuts Pencils are sold by the “gross”. If you buy 1 “gross” you will get 144 pencils.

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

The Mole A counting unit Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 6.02 X 1023 (in scientific notation) This number is named in honor of Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

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.

The Mole 1 dozen cookies = 12 cookies 1 mole of cookies = 6.02 X 1023 cookies 1 dozen cars = 12 cars 1 mole of cars = 6.02 X 1023 cars 1 dozen Al atoms = 12 Al atoms 1 mole of Al atoms = 6.02 X 1023 atoms Note that the NUMBER is always the same, but the MASS is very different! Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

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 “molecules” (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

Calculator 101 The mole in scientific notation is 6.02 x 1023 Type in: 6.022 [2nd] [,] 23 [ee] takes the place of “x 10^”

Dimensional Analysis Process of multiplying by conversion factors to obtain an answer Hinges on : Neatness and Diligence Steps Find the conversion unit between the 2 units Make this conversion unit into 2 fractions Write the 1st number w/ unit Multiply by the fraction (conversion) that cancels Cancel unit Multiply/ Divide #’s

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

Conversion Steps What are you given? What is the end unit? What is the conversion factor? Set-up problem Given x conversion factor = _______end unit Cancel out units Do math Circle your final answer

Example You have 3.5 dozen roses how many actual roses is this? Given: 3.5 dozen End unit roses Conversion factor 1dozen or 12 roses 12 roses 1 dozen 3.5 dozen x 12 roses = ____ roses 1 dozen Cross out matching units

Converting Mole Particles 6.01 mole Na = ? Atoms of Na .75 mol Cl = ? Atoms Cl 8.203 x 1024 atoms O2 = ? Mol O2

Molar Mass Since 1mol always has the 6.02x1023 particles, and (by definition) 1mol 12C has a mass of 12g…then…1mol of 24Mg must have a mass of 1 atom of 12C = 12amu  1mol 12C = 12grams 1atom of 24Mg = 24amu  1mol 24Mg = 24grams 24g

Molar Mass How much does one mole weigh? Would 1 mol of 12C weigh as much as 1mol of 24Mg ? *** Remember: one 12C atom has a mass of 12amu & one 24Mg atom has twice as much mass or 24amu

Molar Mass The Mass of 1 mole (in grams) Equal to the numerical value of the average atomic mass (get from periodic table) 1 mole of C atoms = 12.0 g 1 mole of Mg atoms = 24.3 g 1 mole of Cu atoms = 63.5 g

Molar Mass The mass of a single atom of an element (in amu) is numerically equal to the mass (in grams) of 1mol of that element 1 mol Zn = _____ g 1mol Al = _____ g

atomic mass (amu) = molar mass (grams) Na atoms Pb atoms Molar mass is the mass of 1 mole of in grams Kr atoms Li atoms 1 mole C atoms = 6.022 x 1023 atoms = 12.011 g 1 mole lithium atoms = 6.941 g of Li For any element atomic mass (amu) = molar mass (grams)

Other Names Related to Molar Mass Molecular Mass/Molecular Weight: If you have a single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different. (This is the beauty of Avogadro’s Number!) Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different. THE POINT: You may hear all of these terms which mean the SAME NUMBER… just different units

Conversion factors Moles to mass (grams) Mass (grams) to moles molar mass (periodic table) = grams mole Mass (grams) to moles mole = mole molar mass (grams)

Mass to Atoms and Atoms to Mass 2 steps Mass g (given) to moles Mol to atoms (particles) Mass g (given) x 1mol x 6.02*1023 = atoms mass g (PT) 1 mol Atoms (given) x 1 mol x MM (PT) = grams 6.02*1023 1 mol (atoms)

Do You Understand Molar Mass? How many atoms are in 0.551 g of potassium (K) ? 1 mol K = 39.10 g K 1 mol K = 6.022 x 1023 atoms K 1 mol K 39.10 g K x x 6.022 x 1023 atoms K 1 mol K = 0.551 g K 8.49 x 1021 atoms K 3.2

Moles, n Avogadro’s Number Molar Mass # Atoms Mass, grams

Practice Time Complete practice questions Don’t forget units and sig figs

Mole of compound to mole of individual atoms in the compound Example: How many moles of F atoms are there in 5.5 moles of CCl2F2 ? Given 5.5 moles of CCl2F2 Want atoms of F Need a conversion factor that relates moles of F to moles of compound moles of CCl2F2 x moles of F atoms = moles of F atoms 1 mole of CCl2F2 F2 = 2 moles of F 5.5 moles of CCl2F2 x 2moles of F atoms = moles of F atoms

Practice What is the mass (in grams) of 2.01 x 1022 atoms of S?

Work Time Read section 11.1 pages 309-312 Complete: Practice problems 1-3 on page 311 and 4 on page 312 ***must show all of your work for credit*** Assessment questions 1-10 on page 312