The MoleChapter11

I. Atoms, Molecules, and Formula units

I. Atoms, Molecules, and Formula units

• The terms atom, molecule, and formula units can be used to represent very similar things.

Atoms• The term atoms is used to

describe units of uncombined elements from the periodic table.

Examples: O, U, Zr, and Ag are all atoms (no subscripts)

O

Metals & Non-Metals

Molecules• The term molecule is used to describe a

molecular compound. This is any compound that contains only non-metals in its formula. Non-metals are found on the right side of the staircase on the periodic table, and also includes Hydrogen.

Examples: S8, N2O2, O3, and CO2are all molecules (all non-metals, more than one atom in the formula)

O OC

Formula Units• The term formula units are used to

describe any unit of an ionic compound, which is any compound that contains a metal in its formula. Metals can be found on the left side of the staircase on a periodic table.

Ex. CaO, NaI, and AgNO3 are all formula units (metal in the formula, more than one atom in the formula) OCa

• The term formula units is long, so we’ll call it FUN. We could abbreviate with just the first letter of each word, but that can easily be misinterpreted as something else… yikes, we don’t want that do we?

• Remember, a compound, molecular or ionic, is made up of at least 2 atoms from the periodic table.

Atom, Molecule or FUN?

1) H2O

2) Mg3) NaNO3

4) Cl25) Ne6) SC7) KCl

moleculeatom

Formula Unitmolecule

atom

MoleculeFormula Unit

I. The mole and Avogadro’s number

What is a mole?A machine that bores through hard

surfaces, used especially for tunneling through rock.

A spy who operates from within an

organization, especially a double agent operating against his or her own government from within its intelligence establishment.

An animal

A birth mark

In ChemistryFrom the atomic structure unit we

learned that 1 atom of any element is equal to the atomic mass on the periodic table.

The units for atomic mass is amu (atomic mass unit)

Example: 1 atom of hydrogen = 1.008 amu of hydrogen

• However, in a laboratory it would be difficult to work with atoms, since they are so small

• Instead we use the same atomic masses on the periodic table, but use the units of grams (per mole)

Example: 1 mole of hydrogen =1.008 grams of hydrogen

• The value of the mole was experimentally defined by the number of carbon atoms in 12.01 grams of carbon. There are 6.02 x 1023 atoms of carbon in 12.01 grams of carbon.

• 6.02 x 1023 is referred to as Avogadro’s number. It represents a specific amount of something.

It’s really just a word to represent a

number…

Just like:

• a couple of cookies = __2__ cookies

• a dozen doughnuts = _12_ doughnuts

• a gross of geese = __144___ geese;

• a mole of mints = 6.02 x 1023 mints

• a mole of basketballs = 6.02 x 1023 basketballs

• a mole of marshmallows = 6.02 x 1023 marshmallows

• "mole" represents the number

6.0221367 x 1023 or 602000000000000000000000

• A mole of anything can be difficult to imagine. A mole of marbles is enough to cover the earth to a depth of 50 miles! Whoa, that’s a lot of marbles.

Although a mole can be used to describe any type of object, it is

usually limited to subatomic particles.

• a mole of atoms = 6.02 x 1023 atoms

• a mole of molecules = 6.02 x 1023 molecules

• a mole of formula units = 6.02 x 1023 formula units

Atom, Molecule, & FUN

Molecule = Compound with only Non-Metals(mc or molec)

Formula Unit (FUN) = Compound with a Metal

Atom = single PT element

*don’t abbreviate molecule as mol or mole

In your box…

1 mole = 6.02 X 1023 atoms, molecules,

or formula units

Three ways of representing amounts

• 12 large eggs• 1 dozen eggs• 24 ounces of

eggs

• 6.02 X 1023 Iron atoms

• 1 mole of iron atoms• 55.847 grams of iron

Fun Facts•It is often referred to as Avogadro's number (in honor of Amedeo Avogadro)

•“Mole” is derived from the Latin word moles, which means “a mass”

•“Molecule” is the diminutive form of this word that means “a small mass”

Mole day is generally

celebrated on October 23

1023 AT 6:02AM

get it?

To compare….• A dozen of eggs will fit in an egg

carton

• A mole of eggs will fill all the oceans on the earth more than 30 million times over

It would take 10 billion chickens laying 10 eggs per day more than 10 billion

years to lay a mole of eggs

Why use such a big number?

• We use moles when it comes to atoms and molecules…

• take a guess?

Because atoms are so small

B. Calculating with Avogadro’s Number

• Remember, Avogadro’s number is an equality and you can make 2 conversion factors out of it. Use dimensional analysis to determine

the information you are seeking.

The two conversion factors

1 mol___

6.02 x 1023

*

6.02 x 1023

*

1 mole

and

* = atoms, molecules, or formula units

EX 1: Determine the moles of magnesium there are in 1.23 x 1024

atoms of magnesium

1.23 x 1024 atoms Mg

1 mole Mg

6.02 x 1023 atoms Mg

= 2.04mol Mg

1

G:

W:

R:

1.23 x 1024 atoms Mg

Moles Mg

1 mole Mg = 6.02 x 1023 atoms Mg

When you see atoms, molecules, or FUN in a

problem your relationship is:

1 mol __ = 6.02 x 1023 atom, mc, or fun __

EX 2: Determine the number of atoms in 8.93

moles of argon.

8.93 moles Ar

1 mole Ar

6.02 x 1023 atoms Ar

= 5.38 x 1024Atom Ar

1

G:

W:

R:

8.93 moles Ar

atoms Ar

1 mole Ar = 6.02 x 1023 atoms Ar

Ex 3: Determine the number of water molecules in 11.2 moles of

water.

11.2 moles H2O 6.02 x 1023 molecules H2O

= 6.74 x 1024

1 moles H2O

molecules H2O

1

G:

W:

R:

11.2 moles H2O

Molecules H2O

1 mole H2O = 6.02 x 1023 mc H2O

More Practice

1. Determine the number of atoms in 0.056 mol of

plutonium

0.056 mol Pu

1 mole Pu

6.02 x 1023 atoms Pu

= 3.37 x 1022 Atoms Pu

1

G: 0.056 mol PuW: atoms PuR: 1 mole Pu = 6.02 x 1023 atoms Pu

2. How many moles are in 1.20 x 1025 atoms of

phosphorus?

1.20 x 1025 atoms P

1 mole P

6.02 x 1023 atoms P

=19.9 Moles of Phosphorus

1

G: 1.20 x 1025 atoms PW: moles PR: 1 mole P = 6.02 x 1023 atoms P

3. How many moles are in 5.24 x 1025 molecules of

CCl4?

5.24 x 1025 molec. CCl4

1 mole CCl4

6.02 x 1023 molec. CCl4=87.0Moles CCl4

1

G: 5.24 x 1025 atoms CCl4

W: mc CCl4

R: 1 mole CCl4 = 6.02 x 1023 mc CCl4

Practice Answers

1.

2.

3.

=3.37 x 1022 Atoms Pu

=19.9 Moles of Phosphorus

=87.0Moles CCl4

C. Molar Mass

1. Definition

• molar mass is the mass (in grams) of 1 mole of any element or compound

• units for molar mass: g/molExample: Hydrogen’s molar massis 1.008 g/mol

• the molar mass of any element equals the average atomic mass on the periodic table in grams

Use your periodic table

• 1 mol He = 4.0026 grams He

• 1 mol Ca = 40.08 grams Ca

Other representation for Helium1 mol He = 4.0026

grams He 4.0026 grams 1 mol He

(use a periodic table)

the molar mass of iron is 55.85 g/mol

55.85 g = 1 mole

clean fraction 55.85g Fe1 mol Fe

the molar mass of gold is 196.967g/mol

196.967g Au = 1 mol Au

clean fraction 196.967g Au1 mol Au

•anytime you want to convert from mass (grams) to moles or moles to mass (grams), use molar mass!

Tip: if you see mass (or grams) use your periodic table

B. Calculating with Molar Mass

B. Calculating with molar mass

EX 1: Determine the mass of 3.50 mol of copper.

3.50 mol Cu 63.546g Cu

1 mol Cu

= 222g Cu

1

G:

W:

R:

3.50 moles Cu

Mass Cu (g)

1 mole Cu = 63.546 g Cu

When you see atoms, molecules, or FUN in a

problem your relationship is:1 mol __ = 6.02 x 1023 atom, mc, or fun

__When you see mass in a

problem your relationship is:

1 mol __ = (molar mass) g ___

Ex. 2 Determine the number of moles in 11.9 kg of aluminum.

11.9 kg Al 1000g Al

1 kg Al= 4411 mol Al

26.982g Al

mol Al1

G: 11.9 kg AlW: mol AlR: 1 mole Al = 26.982 g Al 1 kg = 1000 g

G:

W:

R:

11.9 kg Al

Moles Al

1 mole Al = 26.982 g Al1 kg = 1000 g

More Practice

1. Determine the number of moles in 150 g of sulfur

150g S 1 mol S

32.066g S

= 4.68mol S1

G: 150 g SW: mol SR: 1 mole S = 32.066 g S

2. Determine the mass of 8.95 mol of Li

8.95 mol Li 6.941 g Li

1 mol Li= 62.1g Li

1

G: 8.95 mol LiW: mass (g)R: 1 mole Li = 6.941 g Li

3. Determine the mass, in kg, of 12.4 mol of Na.

12.4 mol Na 22.990g Na

1 mol Na

= 0.2851 kg

1000g

kg Na1

G: 12.4 mol NaW: mass (kg)R: 1 mole Na = 22.990 g Na 1 kg = 1000 g

C. Mixed Problems

Tips for solving mole problems

1. If you see “atoms,” “molecules,” or “formula units” mentioned in the problem, write

1 mole X = 6.02 X 1023 atoms, molecules, formula units X .

X = element or compound

Tips for solving mole problems

2. If you see mass involved in the problem, write

1 mol X = (see periodic table) g X

X = element

Ex 1. Determine the mass of

4.56 x 1024 atoms of silver.

4.56 x 1024 atoms Ag

107.868g Ag1 mol Ag

= 817

1 mol Ag6.02 x 1023 atoms Ag

g Ag

1

G: 4.56 x 1024 atoms AgW: mass (g)R: 1 mole Ag = 107.868 g Ag 1 mol Ag = 6.02 x 1023 atoms Ag

Ex. 2 Determine the number of atoms in 100 g of

aluminum

1 mol Al26.982g Al

100 g Al

= 2.23 x 1024

1 mol Al 6.02 x 1023 atoms Al

Atoms Al

1

G: 100 g AlW: atomsR: 1 mole Al = 26.982 g Al 1 mol Al = 6.02 x 1023 atoms Al

More Practice

1. Determine the number of atoms in 0.46 g of copper.

2. Determine the mass (in kg) of 5.98 x 1026 atoms of potassium.

3. Which has more atoms, 26.982 g of aluminum or 4.003 g of helium?

1. Determine the number of atoms in 0.46 g of

copper.

1 mol Cu63.546 g Cu

0.46g Cu

= 4.36 x 1021

1 mol Cu 6.02 x 1023 atoms Cu

Atoms Cu

1

G:

W:

R:

0.46 g Cu

Atoms Cu

1 mole Cu = 6.02 x 1023 atoms Cu

2. Determine the mass (in kg) of 5.98 x 1026 atoms

of K.

5.98 x 1026 atoms K 39.098g K1 mol K

= 38.8

1 mol K6.02 x 1023 atoms K

kg K

1 1000g K

1 kg K

G:

W:

R:

5.98 x 1026 atoms K

kg K

1 mole K = 6.02 x 1023 atoms K1 kg K = 1000 g K

3. Which has more atoms, 26.982 g of aluminum or 4.003 g of

helium?

1 mol Al26.982 g Al

26.982g Al

= 6.02 x 1023

1 mol Al 6.02 x 1023 atoms Al

Atoms Al

1

1 mol He4.003 g He

4.003g He

= 6.02 x 1023

1 mol He 6.02 x 1023 atoms He

Atoms He

1

…I don’t get atoms

A closer look

If 4 grams of helium is equal to one mole of helium atoms

and12 grams of carbon is equal to one

mole of carbon atoms

How can we explain1 mole = 6.02 X x 1023 atoms?

1 mole He 1 mole C 4.006 g/mol 12.001 g/mol6.02 X 1023 atoms He 6.02 X 1023

atoms C

Conclusion

Helium atoms are smaller than carbon

atoms

Don’t forget what you learned before

• What does a mass number of 4 represent?

• Answer: protons + neutrons

Mole and Weight Relationships of Water

and its Parts2 moles + 1 mole = 1

mole H O

H2O                                  

2 * 1.01 g + 16.00 g =

18.02 g

2 moles + 1 mole = 1 mole H O H2O

2 * 1.01 g + 16.00 g =

18.02 g