A Chemist’s Dozen Today you will only need to copy slides that have a TEAL background

Common Measures We frequently refer to measures casually… Couple Few Dozen Baker’s Dozen Ream

Atoms are REALLY small!!! We can’t work with individual atoms or atomic mass units in the LAB – Because we can’t see things that small We work with samples large enough for us to SEE and WEIGH on a balance using units of grams.

This Creates a Problem… Billions of atoms are hard to keep track of in calculations A pile of atoms big enough for us to see contains billions of atoms.

A Chemist’s Dozen It represents a number of ‘things, just like a dozen In honor of Amedeo Avogadro, Italian chemist ( ) Definition of a mole: # of atoms in exactly 12g of Carbon x is referred to as Avogadro’s Number (N A ) 1 mole (symbol: mol) = 6.02 x atoms (or molecules)

The Mole (n) This is a HUGE number!!!! 1 mole = 6.02 x particles, molecules, atoms. 1 dozen eggs =12 Eggs 1 mole of eggs = 6.02 x Eggs

How Big is a Mole? A mole of marbles would cover the entire Earth’s surface 50 MILES DEEP!!!!

How Big is a Mole? If you spent a BILLION DOLLARS every SECOND, you couldn’t spend a mole of dollar bills in your lifetime!!!

How Big is a Mole? If you were able to count at the rate of 1 million numbers a second, it would take about 20 billion years to count out one mole.

Pop Quiz 1 dozen Mg atoms = 1 mole Mg atoms = 1 mole Mg(OH) 2 = 1 mole O 2 = 12 Mg atoms 6.02 x Mg atoms 6.02 x Mg(OH) 2 molecules 6.02 x O 2 molecules

Moles to Particles Calculations

A “dozen” is an easy way to say “12”. A “mole” is an easy way to say “6.02 x 10 23”

There are 268 donuts. How many dozens are present? N = number = 268 donuts D = ? Dozens N D = 12 donuts per dozen D = N = 268 donuts N D 12 donuts/dozen = dozens There are 22 dozens of donuts N D NDND

There are 2.46 x donuts. How many moles are present? N = number = 2.46 x n = moles = ? N A = Avogadro’s number = 6.02 x n = N = 2.46x donuts N A 6.02 x donuts/mol = mol There are 4.09 mol of donuts NANA N n

There are 0.50 mol of methane, CH 4 in a flask. How many molecules are present? n = 0.50 mol N A = 6.02 x molecules/mol N = molecules =? N = n x N A = (0.50 mol)(6.02 x molecules/mol) = 3.01 x molecules There are 3.01 x molecules of methane

In the same sample of methane, determine how many atoms of H are present In 1 molecule of CH 4, there are 4 hydrogen atoms 4 hydrogen = x x = 1.20 x atoms of H *Note* Covalent compounds are composed of molecules. Ionic compounds are composed of formula units ______________ ____________________ 1 molecule CH x molecules

How many molecules are found in 1.25 mol of CO 2 ? n = 1.25 mol N A = 6.02 x molecules/mol N = molecules =? N = n x N A = (1.25 mol)(6.02 x molecules/mol) = x molecules There are 7.52 x molecules of methane

How many atoms are found in 1.25 mol of CO 2 ? n = 1.25 mol N A = 6.02 x molecules/mol N = molecules =? N = n x N A = (1.25 mol)(6.02 x molecules/mol) = x molecules x X 3 atoms = x atoms 1 molecule

How many moles are found in 5.83 x molecules of CO 2 ? n = ? N A = 6.02 x molecules/mol N = 5.83 x molecules n = N/N A = 5.83 x molecules / 6.02 x molecules n = 9.68 mol