THE MOLE... a unit of counting

Quantities in Chemical Reactions

Big Ideas

Relationships in chemical reactions can be described quantitatively

The efficiency of chemical reactions can be determined and optimized by applying an understanding of quantitative relationships in such reactions.

Today

How do chemists calculate and express the number of atoms or molecules in a substance?

How many atoms are in a 27g piece of aluminium foil? Take a guess

How Scientists Keep Track of Atoms How Scientists Keep Track of Atoms • One way to measure how much of a substance is available is to count the # of particles in that sample

• However, atoms & molecules are extremely small

• To solve this problem, scientists developed the concept of the mole

• SYMBOL IS n .• *The mole is a unit song

The Mole

A dozen donuts = 12A mole of donuts = 6.023x1023

a dozen shoes = 12A mole of shoes = 6.023x1023

1 mole = 6.02 x 1023 entities of a substance

1 mole of anything = 6.023x1023

= 602,000,000,000,000,000,000,000!!!

WHAT IS THE MOLE?

Avogadro’s Constant = NA

= 6.023 x 1023 particles1 mol

Units of moles are mol

Different types of particles include:atoms OR molecules OR ions OR electrons OR formula units, etc.

FYI….A formula unit is a term used to represent the lowest whole number ratio of ions in an ionic compound.

On your calculator:EE or EXP or x10^

WHERE DID THIS NUMBER COME FROM?

A mole is the amount of substance that contains as many particles as exactly 12.000g of Carbon-12

The Mole- Examples1 mole of carbon contains 6.02 x

1023 atoms of carbon

1 mole of H2O contains 6.02 x 1023 molecules of H2O

1 mole of NaCl contains 6.02 x 1023 formula units of NaCl

How Big is Avogadro’s Number?

◦ 6.02 x 1023 ÷ 1,000,000 = 6.02 x 1017 d o 6.02 x 1017 d ÷ 365 d/a = 1.65 x 1015 a

If you had one mole of dollars, how long would it take to spend it at a rate of $1,000,000 per day?

Put this into perspective…o The sun is about 4.6 x 109 years old and will burn out in

about 5 x 109 years.o You will need to spend faster!!

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.

The mole is a BIG number.The green pea analogy puts it into

perspective as well:

Did you know that 12 pencils will contain a mole of carbon atoms?

Learning CheckSuppose we invented a new collection unit called a trapp. One trapp contains 8 objects.

1. How many paper clips in 1 trapp?a) 1 b) 4 c) 8

2. How many oranges in 2.0 trapp?

a) 4 b) 8 c) 16

3. How many trapps contain 40 gummy

bears?

a) 5 b) 10 c) 20

How many times would 1 mole of green peas fill the Atlantic ocean?

1. Volume of 1 mol of peas-need to look it up or measure with water displacement/math

Vpea = 0.2mL

V mol pea = 0.2mL x 6.023 . 1023

don’t forget to convert units. In this case mL to L

2. Google Vocean = …..3. Divide …L/….L

Variables to Know

• n = number of moles

• N = number of particles

• NA = Avogadro’s number (6.02 × 1023)

• Two possible types of questions:

o Moles to Particles N = n x NA

o Particles to Moles n = N / NA

N

NA n

Using Avogadro’s Constant

• How many atoms in 2 moles of carbon?N = n x NA

= 2 moles x (6.02 x 1023)

= 1.2 x 1024

particles of C

• How many moles is 5.0 x 1024 particles of iron?n = N / NA

= 5.0 x 1024/6.02 x 1023 = 8.3 moles of Fe

• How many atoms in 2 moles of water?N = n x NA

= 2 moles x 6.02 x 1023 = 1.2 x 1024 molecules of H2O

= 3 atoms per molecule = 3 x (1.2 x 1024 )

= 3.6 x 1024 atoms in 2 moles of H2O

LEARNING CHECK (round to 3 sig. figs.)

How many molecules of CO2 are in 4.56 moles of CO2?

How many moles of water is 5.87 x 1022 molecules?

How many moles is 7.78 x 1024 formula units of MgCl2

How many atoms of carbon are in 1.23 mol of C6H12O6?

Try another… How many electrons are in 1.5 mol of CO2?

2.75 x 1024 molecules

0.0975 mol (or 9.75 x 10-2)

4.44 x 1024 atoms C

12.9 moles

Size of a Mole AssignmentTo better understand the immensity of the

mole you will compare a mole of something to a mole of something else that can be pictured…. BE CREATIVE!!

Eg.Mass of one mole of a substance

How much honey would one mole of bees produce in one season compared to the mass of water in the Atlantic Ocean?

Time to complete one mole of a task

How long would it take in years to blink 6.023 x 1023 times?

Volume of a substance

If you had a mole of green peas covering the earth, how deep would the layer be?

There are 3 parts to this assignment:1. Pick a unique question that compares 1

mole of something to another thing that can be seen visually.

2. Perform the correct calculations3. Make a picture to show the size

comparison4. 1 min presentation

RubricLevel 4 Level 3 Level 2 Level 1

Unique Question that compares 2 things that can be pictured [A-10]

•Question is unique•The entities compared are easily pictured

Calculations are correct and show the size comparison [I-10]Calculations use GRASP & have units [I-10]

•All calculations are correct•All units included•All work logically shown (GRASP)

Picture is creative and shows the size comparison well [C-10]Presented well

•Neat and attractive picture•Size comparison is clear.

Mass to Mole Calculations

Atomic Mass◦Mass of one atom◦Unit μ = atomic mass unit = a.m.u

Eg. Each hydrogen atom has a mass of 1.001μ

◦1 μ equals approximately 1.67 x 10-24g, which is extremely small and not practical to measure.

Enter Molar Mass….

Molar Mass (MM)

The mass of 1 mole of a substance

Mass of 6.023 x 1023 particles

Units are g/mol◦Eg. The molar mass of Hydrogen is 1.01 g/mol

Molar Mass

Molar mass and atomic mass have the same numbers except there is a unit difference.

The g/mol unit is more useful that μ because…It can be measured in the lab using a scale

Atomic Mass Molar Mass

Li 6.94 μ/atom 6.94 g/mol

Ag 107.86 μ/atom 107.86 g/mol

Eg. Find the molar mass of water:H2O H: 2 x 1.001g/mol

O: 1 x 16.00 g/mol18.002g/mol

Eg. Find the molar mass of calcium phosphate:

Ca3(PO4)2 Ca: 3 x 40.08 g/molP: 2 x 30.97 g/molO: 8 x 16.00 g/mol

310.2g/mol

The same as: Gram Molecular Mass (for

molecules) Gram Formula Mass (ionic

compounds) Gram Atomic Mass (for elements)

molar mass is just a much broader term than these other specific masses

Complete the following chart **because this is a chart and not a table you can include

units and calculations in the boxes.

Substance

Type of Particle (atom, molecule, formula unit etc.)

Mass of 6.023 x 1023 particles (Molar Mass)

Atomic Mass (μ)

Ne

O3

C6H12O6

KClO3

Pb

NH3

LiBr

1 Mole in a Beaker Activity Calculate the mass of one mole of each substance. Show your calculations in the

boxes below. Measure out one mole of each substance into a 400mL beaker and draw a line on the beaker in the table to show how much space one mole of that substance takes up.

1 mole of Cu 1 mole of Pb 1 mole of NaCl

1 mole of C12H22O11 1 mole of H2O 1 mole of C

Mole Calculations

MM

m

n

MM = m/n

n = m/MM

m = MMn

Factor Label!

Let the units guide you

N = nNA

n = N/NA

Converting between Mass and Mole

HOMEWORK

pp. 232 #1, 4, 5, 7, 8, 11, 15

Quiz tomorrow – one question from

homework.

A mole is a unit