A New Unit ofMeasurement

A Chemistry Exclusive!!!

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…

• A pile of atoms big enough for us to see contains billions of atoms.

• – Billions of atoms are hard to keep track of in calculations

So chemists made up a new unit

What’s a MOLE?

• It’s a number of things• – Just like a dozen• 1 dozen eggs = 12 eggs• 1 mole eggs = 6.022 x 1023 eggs

Pop Quiz

• 1 dozen Mg atoms =12 Mg atoms• 1 mole Mg atoms =6.022 x 1023 Mg

atoms• 1 mole Mg(OH)2 = 6.022 x 1023

Mg(OH)2 molecules• 1 mole O2 =6.022 x 1023 O2

molecules

Everybody Dance Now!!!

• Moleshake• My moleshake brings all the moles

to the yard,• And they're like, "Man, Chemistry's

hard"• Yeah right, yeah Chemistry's hard,• I can teach you, and I won't even

charge

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.

Avogadro’s Number

• 1 mole = 6.022 x 1023 particles, molecules, atoms.

• 6.022 x 1023 is referred to as Avogadro’s Number

• – In honor of Amedeo Avogadro, Italian chemist (1776-1856)

• 6.022 x 1023 is often symbolized as “NA”

The Mole Song

http://www.youtube.com/watch?v=1R7NiIum2TI&feature=related

Moles to Particles Calculations

There are 268 donuts. How many dozens are

present?• N = number = 268 donuts• D = ? Dozens

• ND= 12 donuts per dozen

D = N = 268 donuts

= 22.333 dozensThere are 22 dozens of donuts

N

D ND

__ _______________

ND 12 donuts/dozen

There are 2.46 x 1024 donuts. How many moles are

present?• N = number = 2.46 x 1024

• n = moles = ?

• NA= Avogadro’s number = 6.02 x 1023

n = N = 2.46x 1024 donuts

= 4.0863787 molThere are 4.09 mol of donuts

NA

N

n

__ ________________

NA 6.02 x 1023 donuts/mol

There are 0.50 mol of methane, CH4 in a flask. How many molecules are present?

• n = 0.50 mol

• NA= 6.02 x 1023 molecules/mol

• N = molecules =?N = n x NA

= (0.50 mol)(6.02 x 1023 molecules/mol)

= 3.01 x 1023 moleculesThere are 3.0 x 1023 molecules of methane

In the same sample of methane, determine how many atoms of H

are present• In 1 molecule of CH4, there are 4

hydrogen atoms4 hydrogen = x

x = 1.20 x 1024 atoms of H

*Note* Covalent compounds are composed of molecules. Ionic compounds are composed of formula units

______________ ____________________

1 molecule CH4 3.01 x 1023 molecules

How many molecules are found in 1.25 mol of CO2?

• n = 1.25 mol

• NA= 6.02 x 1023 molecules/mol

• N = molecules =?N = n x NA

= (1.25 mol)(6.02 x 1023 molecules/mol)

= 7.525 x 1023 moleculesThere are 7.52 x 1023 molecules of carbon

dioxide

How many atoms are found in 2.25 mol of CO2?

• n = 2.25 mol• NA= 6.02 x 1023 molecules/mol• N = molecules =?N = n x NA

= (2.25 mol)(6.02 x 1023 molecules/mol) = 1.355 x 1024 molecules1.355 x 1024 X 3 atoms = 4.06 x 1024

atoms1 molecule

How many moles are found in 5.83 x 1024 molecules of

CO2?• n = ?

• NA= 6.02 x 1023 molecules/mol

• N = 5.83 x 1024 molecules

• n = N/NA

= 5.83 x 1024 molecules / 6.02 x 1023

molecules

n = 9.68 mol

How many moles of lithium oxide are there if you have 1.75 x 1020 Li

atoms?