the mole

The Mole

6.02 X 1023

The Mole

• A counting unit• Similar to a dozen (12), except instead

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

• 6.02 X 1023 (in scientific notation)• This number is named in honor of

Amedeo Avagadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

Mole• A mole is just a number. Just like.....

a pair = 2 a trio = 3

a quartet = 4a dozen = 12

a mole = (mol) 602000000000000000000000

4

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.

How Big is a Mole?

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

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

It would take light 9500 years to travel from the bottom to the top of a stack of 1 mole of $1 bills.

9.12 x 1013

How BIG is a mole?There are ~ 6.6 billion people on Earth

How many Earths would it take to equal the population of 1 mole?

• If you had a mole of cats . . . They would create a sphere larger than Earth!

• If you had a mole of $$$$$ and you spent $800 billion dollars a day how many years would it take to spend a MOLEion dollars?

2.06 x 109 years

• If you had a mole of H2O could you swim in it?

NO!Water molecules are so small

that a mole of H2O = 18ml

How small are atoms?• There are more atoms in one gram of salt than

grains of sand on all the beaches of all the oceans in all the world.

• Just one granule of sugar contains 1 x 1017 molecules

• Each time you take a breath of air, you inhale about 2 x 1022 molecules of nitrogen and 5 x 1021 molecules of oxygen.

• In chemistry we don’t work with single atoms or molecules because they are too small to be weighed or measured

• We have to work with LOTS of atoms in order to measure them

THAT’s WHERE THE

MOLE COMES IN!

Examining Molar Relationships in Balanced Equations

6 CO2 + 12 H2O → 6 O2 + C6H12O6 +6 H20

Balanced equations– Law of conservation of mass / matter

• ATOMS are not created or destroyed during a chemical reaction, they are only rearranged to form new substances.

• # atoms on reactant side = # atoms on product side– The Coefficient for each molecule tells you how many

“moles” of the molecule are in the reaction.• For example: 6 CO2 = 6 moles of CO2

Suppose we invented a new unit called a rapp. One rapp contains 8 objects.

1. How many paper clips in 1 rapp? a) 1 b) 4 c) 8 2. How many oranges in 2.0 rapp?

a) 4 b) 8 c) 16 3. How many rapps contain 40 gummy bears? a) 5 b) 10 c) 20

Learning Check #1

Suppose we invented a new unit called a rapp. One rapp contains 8 objects.

1. How many paper clips in 1 rapp? a) 1 b) 4 c) 8 2. How many oranges in 2.0 rapp?

a) 4 b) 8 c) 16

3. How many rapps contain 40 gummy bears? a) 5 b) 10 c) 20

Learning Check #1 - Answers

The Mole• 1 dozen cookies = 12 cookies• 1 mole of cookies = 6.02 X 1023 cookies

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

• 1 dozen Al atoms = 12 Al atoms• 1 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 (gee, that’s a lot quicker to write, huh?)

= 6.02 x 1023 C atoms = 6.02 x 1023 H2O molecules

= 6.02 x 1023 NaCl “molecules” (technically, ions not molecules)

6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ionsNote that a particle could be an atom

OR a molecule!

A Mole of Particles Contains 6.02 x 1023 particles

1 mole C1 mole H2O1 mole NaCl

6.02 x 1023 particles 1 mole

or

1 mole 6.02 x 1023 particles

Note that a particle could be an atom OR a molecule!

Avogadro’s Number as Conversion Factor

1. Number of atoms in 1.0 mole of Al a) 500 Al atoms b) 6.02 x 1023 Al atoms c) 3.01 x 1023 Al atoms

2. Number of moles of S in 6.02 X 1023 S atoms a) 1.0 mole S atoms b) 6.02 mole S atoms c) 1 x 1023 mole S atoms

Learning Check #2

1. Number of atoms in 1.0 mole of Al a) 500 Al atoms b) 6.02 x 1023 Al atoms c) 3.01 x 1023 Al atoms

2. Number of moles of S in 6.02 X 1023 S atoms a) 1.0 mole S atoms b) 6.02 mole S atoms c) 1 x 1023 mole S atoms

Learning Check #2 - Answers

STOICHIOMETRY- the study of the

quantitative (#) aspects of chemical reactions.

• The Mass of 1 mole in grams• Equal to the numerical value of the average

atomic mass. This number is found on the periodic table, below the symbol for each element.

Molar Mass

Molar MassThe Atomic Mass # does not have units in the periodic table. Often, chemists use “amu” for the atomic mass unit. To determine the molar mass, we change “amu” into “grams/mole”

1 amu = 1 gram 1 mole

1 mole of He atoms = 4.0 g

1 mole of C atoms = 12.0 g

1 mole of Mg atoms = 24.3 g

1 mole of Cu atoms = 63.5 g

check on your periodic table!!!

Find the molar mass for the following elements:(round to the tenths place for decimals)

Learning Check #3

A. 1 mole of Br atoms

B. 1 mole of Sn atoms

C. 2 moles of C atoms

Find the molar mass for the following elements:(round to the tenths place for decimals)

Learning Check #3 - Answers

A. 1 mole of Br atoms

B. 1 mole of Sn atoms

C. 2 moles of C atoms

= 79.9 g/mol

= 118.7 g/mol

= 12 g/mole * 2 moles = 24 g/mol

ADD UP THE MASS FROM ALL ATOMS IN THE MOLECULE !!!!!

***The subscript tells you how many atoms for each element are present in the molecule

1 mole of the molecule CaCl2 = 111.1 g/mol

HOW????

1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl

Molar Mass of Molecules & Compounds

Learning Check #4

What is the Molar Mass of the molecule K2O?****Units = g/mol

Learning Check #4 - Answers

What is the Molar Mass of the molecule K2O?****Units = g/mol 2 moles of K = 39 g/mol * 2 = 78 g/mol + 1 mole of O = 16 g/mol

TOTAL = 94 g/mol !!!!

What is Dimensional Analysis?Dimensional analysis is just a fancy name

for a method of calculating that:

1. uses numbers in the form of fractions.2. lets us convert from one type of unit

measurement to another.3. In chemistry, this lets us convert from

moles to grams or visa-versa

What is a Unit?A unit is something that gives definition

to a numerical value, quantity, or measurement.

• Length : meters, centimeters, feet, inches, miles, kilometers• Mass : Kilograms, grams, pounds• Time : hours, minutes, seconds, days,

months• Volume : cups, teaspoons, liters,

milliliters, gallons, quarts• Currency: dollars, cents, dimes

Turning Numbers (or quantities) into fractions called conversion factors:

a ratio of equivalent measurements. ©Prentice Hall

Conversion Factors Conversion factors can be written in 2

ways:

The unit you want goes on top or the numerator and the unit you want to cancel goes on the bottom or denominator.

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

Converting Moles and Grams

1. Molar mass of Al 1 mole Al = 27.0 g Al

2. Conversion factors for Al

27.0 g Al or 1 mol Al 1 mol Al 27.0 g Al

Why? Because I want to “cancel” mol and be left with g. g must be on top.

3. Setup 3.00 moles Al x 27.0 g Al 1 mole Al4. Math 3 * 27/1 = 815. Answer = 81.0 g Al