The Mole What's a mole? In chemistry, a mole is a counting unit. What does that mean? 1 dozen = 12 units(ie eggs,donuts) 1 mole = 6.02x1023 particles. That's 602,000,000,000,000,000,000,000 particles! 6.02x1023 is Avogadro's Number A mole is used to represent lots of particles atoms molecules(covalent compounds) ions Forumula Units (ionic compounds) 1

The Mole If you have 3 particles of water, what do you have? You have 3 water molecules because H2O is molecular Covalently bonded compounds are called molecules If you have 4 particles of table salt, what do you have? You have 4 NaCl formula units becauseNaCl is ionic Ionic compounds are called formula units If you have 5 particles of gold, what do you have? You have 5 gold atoms because gold is an element Atoms are the unit for elements 2

The Mole How do you represent 6.02x1023 in a scientific calculator? You can type 6.02x10^23 if you want... but there's a better way! - For graphing calculators: Type in 6.02 then the 2nd button, then the “,” button, then 23 The calculator will display 6.02E23 This means “6.02x1023” to the calculator. - For other calculators there is usually a key marked “E” or “EXP” that allows you to enter numbers in scientific notation. 3

How BIG is Avagadro's Number? 6.02x1023 dollars would be enough to give every person on Earth $87 trillion. That’s $1 million a second for the next 2.8 years. A modern computer that can make up to 100 million counts per second would take almost 200 million years to count to 6.02x1023 If 6.02x1023 snowflakes fell evenly across the United States, the blanket of snow would cover every building in the country, including the tallest skyscrapers. If you could travel at the speed of light (186,000 mi/s in a vacuum), it would take you more than 100 billion years (longer than the Universe has been around) to travel 6.02x1023 miles. 4

Moles & Particles If 1 mole = 6.02 x 1023, then we can determine how many atoms(or molecules) are in stuff. 1 mole : 6.02 x 1023 Or 1 mol 6.02 x 1023 particles How many silver atoms are in 3 moles of Ag? (using dimensional analysis (factor method)) 3 mol Ag x 6.02 x 1023 atoms Ag = 1mol Ag Waitaminute… but why are moles on the bottom and Avogadro’s number on the top? Since 1mol = 6.02x1023, either one can be on top, we just choose the one that will cancel out the original unit. 5

Mole to Particle Conversions Examples: How many molecules of methane are in 4.50 mol of methane? 4.50 mol CH4 x 6.02x1023 molecules CH4 1 mol CH4 = 2.71x1024 molecules CH4 How many moles of iron are in 2.39x1024 iron atoms? 1 mol Fe = 6.02x1023 Fe atoms 2.39x1024 atoms Fe x 1 mol Fe 6.02x1023 atoms Fe = 3.97 mol Fe 6

Molar Mass Atomic measures the mass of atoms Really small! Atomic Mass is based on Carbon-12 (12C) Very abundant, bonds with most everything 1 amu = 1/12 the mass of 12C Too small to count Scientists decided that if 12C = 12 amu, then 12 grams of carbon = 1 mole of carbon. Which is equal to 6.02x1023 atoms of carbon 1 mole of anything = its atomic mass in grams 1 atom of oxygen = 16.00 amu 1 molecule of H2O = 18.02 amu 1 formula unit of NaCl = 58.44amu 1 mole of oxygen = 16.00 grams 1 mole of H2O = 18.02 grams 1 mole of NaCl = 58.44 grams 7

Moles & Particles Molar Mass = the mass in grams of 1 mole of any substance. AKA gram-formula mass Unique for every substance Unit: grams per mole (g/mol) Calculations with Molar Mass What is the mass in grams of 2 mole of iron? molar mass of Fe = 55.85 g/mol 2 mol Fe x 55.847grams Fe = 111.60 grams Fe 1 mol Fe 8

Mole/Mass Calculations Examples: 1. What is the mass of 0.250 moles of magnesium? Using Periodic Table: 1 mol Mg = 24.31g Mg 2. What is the mass of 5.80 moles of carbon monoxide? Molar mass of CO = 28.01g/mol 24.305 g Mg = 6.08 g Mg 0.250 mol Mg x 1 mol Mg 28.01 g CO = 162 g CO 5.80 mol CO x 1 mol CO 9

Mole/Mass Calculations Examples: 1. How many moles would 50.45 grams of neon be equal to? 1 mol Ne = 20.18g Ne 2. How many moles would 134.0 grams of methane(CH4) be equal to? Molar mass of methane = 16.05 g/mol 1 mol Ne = 2.500 mol Ne 50.45g Ne x 20.18g Ne 1 mol CH4 = 8.349 mol CH4 134.0g CH4 x 16.05g CH4 10