The Mole "Not everything that counts can be counted, and not everything that can be counted counts." Albert Einstein

What is a mole? The mole is a counting unit. Like . . . So then ... 1 dozen = 12 each 1 yard = 3 feet 1 cup = 8 ounce So then ... 1 mol = 6.022 x 1023 particles That’s Avogadro’s Number!

Where did it come from? Mole (n) is the SI unit for the number of particles Amedo Avogadro determined the number of particles in a mole The mole is the measure of the amount of a substance whose number of particles is the same as 12 grams of Carbon -12

Calculations Using dimensional analysis you can determine the number of particles in a mole 1 mole = 6.022 x 1023 particles, molecules, etc. 1 mole / 6.022 x 1023 particles 6.022 x 1023 particles / 1 mole

So, let’s count . . . 1 mol of Ag = 1 mol of CO2 = 1 mol of pizza = 6.022 x 1023 atoms Ag 1 mol of CO2 = 6.022 x 1023 molecules of CO2 1 mol of pizza = 6.022 x 1023 pizzas!

Calculating # moles 3.011 x 1023 atoms of Oxygen 0.5 moles of Oxygen 3.655 x 1012 molecules of CO 6.070 x 10-10 moles of CO

Classwork Practice on these pg. 228 #1-4 pg. 229 #1-5

Atomic Mass The mass of an element at rest. Relative Atomic Mass is the weighted average of all the atomic masses for all of the isotopes of an element. Since the atomic mass is an average, it is not in whole number form.

Atomic Mass Unit Atomic mass is measured in atomic mass units (amu) as a standard It equals the measure of 1/12 the mass of 12 grams of Carbon-12 1 a.m.u. = 1.6605 x 10-27kg

For Example The periodic chart list the atomic mass of Oxygen as 15.999 amu Does Oxygen really weigh 15.999 g?

Calculate the Mass of an Atom Oxygen has an atomic mass of 15.999 amu 1 amu = 1.6605 x 10-27 kg So 1 atom of Oxygen really weighs, 15.999 a.m.u. x (1.6605 x 10-27kg a.m.u.) = 2.657 x 10-26 kg or 2.657 x 10-23 g

Determine the Atomic Mass What is the atomic mass in amu of Sodium? Mass number = 22.989, so . . Atomic mass = 22.989 amu What is the atomic mass in amu of Uranium? 238.03 amu

Formula Mass Chemical compounds are written as an empirical formula. Ex. H2SO4 is Sulfuric Acid To calculate atomic mass, add each atom. H = 1.008 x 2 = 2.016 S = 32.07 x 1 = 32.07 O = 15.999 x 4 = 63.996 Total Atomic Mass = 2.016+32.07+63.996 = 98.08 amu

Molar Mass One mole of particles has a special mass associated with it. Molar mass is grams per mole g/mol The number is represented by the mass number on the Periodic Chart

So, then . . . If the mass number on the periodic chart for Oxygen is 15.999, Then Oxygen has a molar mass of . . . 15.999 grams per mole

What is the molar mass of ... Oxygen? Nitrogen? Carbon?

Molar Formula Mass The subscripts in a chemical formula represent the number of moles of that element each separate element contributes to the overall formula mass of a chemical compound Example: H2O H = 1.011 x 2 = 2.022 g/mol O = 15.999 g/mol H2O = 18.000 g/mol

Classwork Now try these in class p. 231 # 1-4 p. 233 # 6-13

Periodic Mass Number The mass number on the Periodic Chart can be the weight of a single atom in atomic mass units; (15.999 amu Oxygen) OR The mass of one mole of the element (15.999 g/mol Oxygen)

And . . . If Oxygen is 15.999 g/mol; and, 1 mol = 6.022 x 1023 atom, then . . . (15.999 g/mol) x (1 mol/6.022 x 1023 atom) = 2.657 x 10-23grams

(15.999 g/mol) x (1 mol/6.022 x 1023 atom) = Wait a minute! Have you seen that number before? Let’s recap . . . 15.999 a.m.u. x (1.6605 x 10-27kg a.m.u.) = 2.657 x 10-26 kg or 2.657 x 10-23 g And (15.999 g/mol) x (1 mol/6.022 x 1023 atom) = 2.657 x 10-23grams

Moles to Mass Conversions Moles = mass (g) / Molar mass (g/mol) n = m / M

Let’s Calculate Calculate the number of moles in 250 g of Copper Molar mass of Cu = 63.55 g/mol n = m / M n = 250 g / 63.55 g/mol = 3.94 mol Cu

And another . . . Calculate the mass of 3.50 mol of Cu Molar mass of Cu is 63.55 g/mol n = m / M and m = n * M m = 3.50 mol * 63.55 g/mol = 222 g Cu