Warm-up: Intro activity

1. Determine, to the greatest precision and accuracy possible, the thickness of a piece computer paper?

2. Determine which of the following has the most amount of pieces (not necessarily worth the most money). Do you need any more information?

a) 1 kg of penniesb) 1 kg of nickelsc) 1 kg of dimes

3. Brainstorm as many words as you can that are directly related to numbers (for example, 1 dozen=12)

coefficients give ratios

coefficients of a balanced equation give the ratio of molecules in the reaction

2H2 (g) + O2 (g) 2 H2O (l)

___ molecules of hydrogen gas react with ___ molecules of oxygen gas to give ___ molecules of water

2 hydrogen molecules 1 oxygen molecule

2 water molecules

Correct Ratio of molecules 2H2 : 1O2 : ?H2O

1 hydrogen molecule 1 oxygen molecule

?

Wrong Ratio of molecules 1H2 : 1O2 : ?H2O

Problems in chemistry…

• Atoms are too small to talk about and measure easily

• Atoms of different elements have different masses (periodic table)

Also…• Can you “measure out” 2 molecules of

hydrogen and 1 molecule of water??? Why or why not???

What do unit do we use to measure?

How many molecules are in one gram?

Since one gram contains a huge amount of molecules or atoms...

chemists have devised a special counting unit to understand the large numbers of molecules or atoms measured

in the lab. This unit is called the mole!

What is a “counting unit”?

• Bakers use the counting unit “dozen” to understand they have 12 donuts

• Pencils are sold by the “gross”. If you buy 1 “gross” you will get 144 pencils.

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Suppose we invented a new collection 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 CheckLearning Check

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The MoleThe Mole• A counting unit• Similar to a dozen, 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 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

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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.

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The MoleThe 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?)

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= 6.02 x 1023 C atoms

= 6.02 x 1023 H2O molecules

= 6.02 x 1023 NaCl “molecules”(technically, ionics are compounds not molecules so

they are called formula units)

6.02 x 1023 Na+ ions and

6.02 x 1023 Cl– ions

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

1 mole C

1 mole H2O

1 mole NaCl

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Calculator 101

• The mole in scientific notation is 6.02 x 1023

• Type in:– 6.022– [2nd]– [,]– 23

• [ee] takes the place of “x 10^”

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Dimensional Analysis

• Process of multiplying by conversion factors to obtain an answer

• Hinges on :– Neatness and

Diligence

Steps1. Find the conversion unit

between the 2 units2. Make this conversion

unit into 2 fractions3. Write the 1st number w/

unit4. Multiply by the fraction

(conversion) that cancels 5. Cancel unit6. Multiply/ Divide #’s

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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 Avogadro’s Number as Conversion FactorFactor

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Conversion Steps

1. What are you given?

2. What is the end unit?

3. What is the conversion factor?

4. Set-up problemGiven x conversion factor = _______end unit

5. Cancel out units

6. Do math

7. Circle your final answer

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Example

• You have 3.5 dozen roses how many actual roses is this?

1. Given: 3.5 dozen

2. End unit roses

3. Conversion factor 1dozen or 12 roses

12 roses 1 dozen

4. 3.5 dozen x 12 roses = ____ roses

1 dozen

5. Cross out matching units

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Converting Mole Particles

• 6.01 mole Na = ? Atoms of Na

• .75 mol Cl = ? Atoms Cl

• 8.203 x 1024 atoms O2 = ? Mol O2

Molar Mass

Since 1mol always has the 6.02x1023 particles, and (by definition) 1mol 12C has a mass of 12g…then…1mol of 24Mg must have a mass of

1 atom of 12C = 12amu 1mol 12C = 12grams

1atom of 24Mg = 24amu 1mol 24Mg = 24grams

24g

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Molar Mass

How much does one mole weigh?

Would 1 mol of 12C weigh as much as 1mol of 24Mg ?

*** Remember: one 12C atom has a mass of 12amu & one 24Mg atom has twice as much mass or 24amu

• The Mass of 1 mole (in grams)

• Equal to the numerical value of the average

atomic mass (get from periodic table)

1 mole of C atoms = 12.0 g

1 mole of Mg atoms = 24.3 g

1 mole of Cu atoms = 63.5 g

Molar MassMolar Mass

Molar Mass

The mass of a single atom of an element (in amu) is numerically equal to the mass (in grams) of 1mol of that element

1 mol Zn = _____ g

1mol Al = _____ g

Molar mass is the mass of 1 mole of in gramsNa atomsPb atoms

Kr atoms Li atoms

1 mole C atoms = 6.022 x 1023 atoms = 12.011 g

1 mole lithium atoms = 6.941 g of Li

For any element

atomic mass (amu) = molar mass (grams)

Other Names Related to Molar MassOther Names Related to Molar Mass

• Molecular Mass/Molecular Weight: If you have a single

molecule, mass is measured in amu’s instead of grams. But,

the molecular mass/weight is the same numerical value as 1

mole of molecules. Only the units are different. (This is the

beauty of Avogadro’s Number!)

• Formula Mass/Formula Weight: Same goes for

compounds. But again, the numerical value is the same.

Only the units are different.

• THE POINT: You may hear all of these terms which mean the SAME NUMBER… just different units

Conversion factors

• Moles to mass (grams) molar mass (periodic table) = grams

mole

• Mass (grams) to moles

mole = mole

molar mass (grams)

Mass to Atoms and Atoms to Mass

• 2 steps– Mass g (given) to moles – Mol to atoms (particles)

Mass g (given) x 1mol x 6.02*1023 = atoms mass g (PT) 1 mol

Atoms (given) x 1 mol x MM (PT) = grams 6.02*1023 1 mol

(atoms)

Do You Understand Molar Mass?

How many atoms are in 0.551 g of potassium (K) ?

1 mol K = 39.10 g K

1 mol K = 6.022 x 1023 atoms K

0.551 g K 1 mol K39.10 g K

x x 6.022 x 1023 atoms K1 mol K

=

8.49 x 1021 atoms K

3.2

Molar MassAvogadro’s Number

Practice Time

• Complete practice questions

• Don’t forget units and sig figs

Mole of compound to mole of individual atoms in the compound

• Example: How many moles of F atoms are there in 5.5 moles of CCl2F2 ?

• Given 5.5 moles of CCl2F2

• Want atoms of F• Need a conversion factor that relates moles of F to moles of

compound

• moles of CCl2F2 x moles of F atoms = moles of F atoms

1 mole of CCl2F2

• F2 = 2 moles of F

• 5.5 moles of CCl2F2 x 2moles of F atoms = moles of F atoms

1 mole of CCl2F2

Practice

What is the mass (in grams) of 2.01 x 1022 atoms of S?

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Work Time

• Read section 11.1 pages 309-312

• Complete:– Practice problems 1-3 on page 311 and 4 on

page 312 ***must show all of your work for credit***

– Assessment questions 1-10 on page 312