Unit 8 The MoleUnit 8 The Mole

6.02 X 6.02 X 10102323

The MoleThe MoleA counting unitSimilar to a dozen, except instead

of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000

Avogadro’s number: 1 mole= 6.02 x 1023 particles (in scientific notation)

This number is named in honor of Amedeo Avogadro (1776 – 1856)Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

Just How Big is a Mole?Just How Big is a Mole?Enough soft drink cans to cover the

surface of the earth to a depth of over 200 miles.

If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.

If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 milliontimes.

One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles.

HomeworkHow long will it take to spend a mole of

Lps.1.00 if they were being spent at a rate of a billion per second?

The MoleThe Mole1 dozen cookies = 12 cookies1 mole of cookies = 6.02 X 1023 cookies

1 dozen cars = 12 cars1 mole of cars = 6.02 X 1023 cars

1 dozen Al atoms = 12 Al atoms1 mole of Al atoms = 6.02 X 1023 atoms

Note that the NUMBER is always the same, but the MASS is very different!

Mole is abbreviated mol (big difference!!)

A Mole of ParticlesA Mole of Particles Contains 6.02 x 1023 particles

= 6.02 x 1023 C atoms

= 6.02 x 1023 H2O molecules

= 6.02 x 1023 NaCl formula units(ionic compounds are not molecules so they are

called formula units)

6.02 x 1023 Na+ ions and

6.02 x 1023 Cl– ions

1 mole C

1 mole H2O

1 mole NaCl

Avogadro’s Number as Conversion Avogadro’s Number as Conversion FactorFactor

6.02 x 1023 particles 1 mole

or

1 mole

6.02 x 1023 particles

Note that a particle could be an atom, ion, formula unit

OR a molecule!

Ex. 1 How many atoms are in 0.67mol of Al?= 0.67 mol Al 6.02x 1023 atoms Al 1 mol Al

= 4.0 x 1023 atoms Al

Remember to round answer to correct number of significant digits and don’t forget to write units

Ex. 2 A sample of gold contains 5.21 x1023 atoms of gold, how many moles is this?= 5.21x 1023 atoms Au 1 mol Au

6.02x 1023 atoms Au

= 0.865 mol Au

Remember to round answer to correct number of significant digits and don’t forget to write units

Learning CheckLearning Check

1. Number of atoms in 0.500 mole of Aga) 500 Ag atoms

b) 6.02 x 1023 Ag atomsc) 3.01 x 1023 Ag atoms

2.Number of moles of S in 1.8 x 1024 S atomsa) 1.0 mole S atomsb) 3.0 mole S atomsc) 1.1 x 1048 mole S atoms

Learning CheckLearning Check

1. Number of atoms in 0.500 mole of Aga) 500 Ag atoms

b) 6.02 x 1023 Ag atomsc) 3.01 x 1023 Ag atoms

2.Number of moles of S in 1.8 x 1024 S atomsa) 1.0 mole S atomsb) 3.0 mole S atomsc) 1.1 x 1048 mole S atoms

CW p 323-4 #1-6

Molar MassMolar MassThe Mass of 1 mole (in grams)

For atoms: equal to the numerical value of the average

atomic mass (get from periodic table, round to the

tenth)

1 mole of C atoms = 12.0 g

1 mole of Mg atoms = 24.3 g

1 mole of Cu atoms = 63.5 g

Units: grams/mole or g/mol

Other names for molar mass:

Molecular Mass/Molecular Weight

Formula Mass/Formula Weight

Learning Check!Learning Check!Find the molar mass

(usually we round to the tenths place)

A.1 mole of Br atomsB.1 mole of Sn atoms

= 79.9 g/mole

= 118.7 g/mole

Molar Mass of Molecules and Molar Mass of Molecules and CompoundsCompounds

The molar mass of a compound is equal to the sum of the atomic masses of all the atoms in the compound.

1 mole of CaCl2 = 111.1 g/mol

1 mole Ca x 40.1 g/mol = 40.1 g/mol

+ 2 moles Cl x 35.5 g/mol = 71.0 g/mol

= 111.1 g/mol CaCl2

Molar mass for calcium nitrate, Ca(NO3)2

Ca : 1 atom x 40.1 g/mol = 40.1 g/mol

N: 2 atoms x 14.0 g/mol = 28.0 g/mol

O: 6 atoms x 16.00 g/mol = 96.0 g/mol

+164.1 g/mol

Learning Check!Learning Check!

A. Molar Mass of K2O = ? Grams/mole

B. Molar Mass of antacid Al(OH)3 = ? Grams/mole

Learning Check!Learning Check!

A. Molar Mass of K2O = ? Grams/mole

K : 2 x 39.1 = 78.2

O : 1 x 16.0 = 16.0

+

94.2 g/ mol

B. Molar Mass of antacid Al(OH)3 = ? Grams/mole

Al: 1 x 27.0 = 27.0

O: 3 x 16.0 = 48.0

H: 3 x 1.00 = 3.0

+

78.0 g/mol

Learning CheckLearning Check

Prozac, C17H18F3NO, is a widely used

antidepressant that inhibits the uptake of

serotonin by the brain. Find its molar mass.

(answer: 304 g/mol)

cw p335 #34-36

Calculations with Molar MassCalculations with Molar Mass

molar mass Grams Moles

To convert between grams and moles, use the molar mass of the substance as a conversion factor.

Ex. 1 Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al?

3.00 moles Al ? g Al To convert between grams and moles, calculate the molar mass of the substance

Molar mass of Al 1 mole Al = 27.0 g Al

Setup 3.00 moles Al x 27.0 g Al 1 mole Al

Answer = 81.0 g Al

2. Acetylsalicylic acid is the chemical name for the substance we commonly know as aspirin, C6H4(OCOCH3)CO2H. How many moles of aspirin are 255g of aspirin?

255 g aspirin ? Mol aspirin

1. Molar mass of aspirin

1 mole = 180.0 g aspirin

2. Setup 255 g aspirin x 1 mole aspirin180 g aspirin

Answer = 1.42 mol aspirin

Learning Check!Learning Check! The artificial sweetener aspartame (Nutra-

Sweet) formula C14H18N2O5 is used to sweeten

diet foods, coffee and soft drinks. How many

moles of aspartame are present in 225 g of

aspartame?

Answer: 0.765 mol aspartame

Learning CheckA recipe requires 0.629 mol of sucralose,

SPLENDA (C12H19Cl3O8). How many grams is this?

Answer: 250. g splenda

CW: p328-9 #15-18; p336-7 #37-41

Conversions: particles Conversions: particles Grams Grams 6.02 X 1023 particles = 1 mole

AND

1 mole = molar mass (grams)

We can convert between particles and grams (Two step process)

You can’t go directly from atoms to grams!!!! You MUST go thru MOLES.

Calculations : mole road mapCalculations : mole road map

Mole (mol)

Particles (atoms, ions, molecules, formula units)

Mass (g)

÷Molar mass

Molar mass x

AVOGADRO’S

NUMBER

x Avogadro’s number

MOLAR

MASS (g/m

ol)

Avogadro’s ÷ number

Atoms/Molecules and GramsAtoms/Molecules and GramsHow many atoms of Cu are present in 35.4 g of Cu?

Plan: g Cu mol Cu atoms Cu

Step 1: converting g Cu to mol Cu using molar mass

35.4 g Cu 1 mol Cu = 0.5566 mol Cu

63.6 g Cu

Step 2: converting mol Cu to atoms Cu using Avogadro’s number.

0.5566 mol Cu 6.02 x 1023 atoms Cu= 3.35x1023 atoms Cu

1 mol Cu

Atoms/Molecules and GramsAtoms/Molecules and GramsHow many atoms of Cu are present in 35.4 g of Cu?

Plan: g Cu mol Cu atoms Cu

Combining step 1 and 2

35.4 g Cu 1 mol Cu 6.02 x 1023 atoms Cu= 3.35x1023 atoms Cu

63.6 g Cu 1 mol Cu

Atoms/Molecules and GramsAtoms/Molecules and GramsWhat is the mass of 5.54x1024 molecules of CO?

Plan: molecules CO mol CO g CO

Step 2: converting mol CO to g CO using molar mass

9.2026 mol CO 28.0 g CO = 258g CO

1 mol CO

Step 1: converting molecules CO to mol CO using Avogadro’s number.

5.54x1024 molecules of CO 1 mol CO = 9.2026 mol CO

6.02x1023 molecules CO

Learning Check!Learning Check!How many atoms of K are present in 78.4 g of

K? (answer: 1.21 x 1024 atoms K)

78.4 g K 1 mol K 6.02 x 1023 atoms K= 1.21x1024 atoms K

39.1 g K 1 mol K

Learning Check!Learning Check!What is the mass (in grams) of 1.20 X 1024 molecules

of glucose (C6H12O6)? (answer:359 g glucose)

1.20 x 1024 molecules glucose 1 mol glucose 180 g glucose

6.02x1023 molecules 1 mol glucose

glucose

= 359g