The Mole Concept Introduction Number of Particles, Moles, and Mass

Dimensional Analysis starting with one unit of measurement and ending up with a different one “cancel out” what you don’t want use conversion factors (fraction that equals one) the numerator will contain the unit you want the denominator will contain the unit you are trying to get rid of try to predict a “ball park answer” if possible so you might recognize a wrong answer

sometimes they can be done in one step example: 23,532 seconds = ? minutes 23,532 sec. X 1 min sec min.

sometimes they take multiple steps example: 23,532 seconds = ? hours 23,532 sec. X 1 min. X 1 hour = 1 60 sec. 60 min hours

but if you don’t know the conversion factor(s), the problem becomes impossible example: 750 ml = ? fl oz 750 ml X 1 fl oz ml 25.3 fl oz

LecturePLUS Timberlake How many minutes are in 2.5 hours ? Initial unit 2.5 hr Conversion Final factor unit 2.5 hr x 60 min = 150 min 1 hr cancel Answer (2 SF)

What is wrong with the following setup? 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min How many seconds are in 1.4 days?

1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min Units would be = day 2 (sec)/hr 2 Not the final unit needed How many seconds are in 1.4 days?

Measuring Matter By counting  simply a number or moles By determining the mass  grams By determining the volume  liters

Not these! Not this! The Mole

Counting particles simply a number or moles

the mole is a unit used in chemistry to represent a large number of particles such as… atoms (Ne, Ar…) molecules (H 2 O, CO 2 …) ionic compounds (NaCl, MgCl 2 …) ions (Mg 2+, Cl 1- …) similar to a dozen, except instead of 12, it’s 602 billion trillion 6.02 x or 602,214,199,000,000,000,000,000 known as Avogadro’s number

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

1 mole C  6.02 x C atoms 1 mole water  6.02 x H 2 O molecules 1 mole NaCl  6.02 x NaCl ionic compounds (formula units) 6.02 x Na + ions 6.02 x Cl – ions

for counting in chemistry, the conversion factor will be: 1 mole 6.02 x particles OR 6.02 x particles 1 mole Note that a particle could be an atom OR a compound OR a molecule!

Number of particles to moles How many moles in 5.68 x fluorine molecules? 5.68 x F 2 molecules x _____1 mole____ x molecules = 94.4 mol F 2

How many moles of water in 7.77x10 24 molecules of water? 7.77 x molecules H 2 O x 1mole 6.02x10 23 molecules = 12.9 moles H 2 O

Number of moles to particles How many atoms in 5.59 moles of He? 5.59 moles He x 6.02 x atoms 1 1 mole = 3.36 x atoms How many atoms in 2.98 moles of H 2 0 molecules ? 2.98 moles x 6.02 x molecules H 2 O x 3 atoms 1 1 mole 1 molecule H 2 O = 5.38 x atoms

Measuring mass in grams

molar mass this is how many grams you would have in a mole of a substance simply change atomic mass from the periodic table for the element/molecule/ compound to grams oxygen’s atomic mass is amu therefore 1 mole of oxygen has a molar mass is g/mol sugar’s (C 6 H 12 O 6 ) atomic mass is amu carbon: 12.00(6) = hydrogen: 1.00(12) = oxygen: 16.00(6) = therefore 1 mole of sugar has a molar mass of g/mol

Calculate the Molar Mass of Na 3 PO 4. Atom#Atomic MassTotal Na3X 23.0=69.0 P1X 31.0=31.0 O4X 16.0=64.0 Total=164.0 Therefore the molar mass is g mol -1

Give the molar mass (mass of one mole): Fe → 55.9 g/mol C 2 H 6 → 30.1 g/mol Fe(OH) 2 → 89.9 g/mol C 12 H 22 O 11 → g/mol CuSO 4 · 5 H 2 O → 238 g/mol

conversion factor will be:  1 mole molar mass OR  molar mass__ 1 mole Converting Moles to Grams and Grams to Moles

Find the mass (in grams) of 1.93 moles of MgO? 1.93 mol MgO x 40.3 g MgO 1 1 mol MgO = 77.8 g MgO Find the number of moles in 23.5 g of MgO? 23.5 g MgO x 1 mole MgO g MgO = mol MgO Number of moles to mass(g) Mass(g) to moles

Number of grams to moles to particles Find the number of particles in 13.9 g of MgO? 13.9 g MgO x 1 mole MgO_ x _6.02 X particles MgO g MgO 1 mole MgO 1 mole MgO_ x _6.02 X particles MgO 40.3 g MgO 1 mole MgO 6.02 X particles MgO 40.3 g MgO molar mass (g) = 2.07 X particles of MgO here it is again combining two conversion factors same thing but be careful if you do this!

What is the mass of 2.55 × atoms of lead? = 87.8 g Pb 2.55 × atoms Pb × 1 mol Pb 6.02×10 23 atoms Pb g Pb 1 mole Pb ×

How many atoms in 22 grams of copper?

The Mole Road Map Mass “Stuff” Mole Volume g mole g mole x mole 22.7 L mole mole L Stuff: Atoms Molecules Particles Electrons Ions Formula Units For Gases STP (Standard Temp & Pressure) (0 o C (273 K) & 1 atm)