The Mole Concept

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Counting Atoms

••

Chemistry is a

quantitative

sc

sciien

encce -

e - w

we

e

need a "counting unit."

••

The

MOLE

••

1 mole is the amount of substance that

contains as many particles (atoms or

molecules) as there are in 12.0 g of C-12.

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The Mole is Developed

C

Caarrbboon n AAttoommss HHyyddrrooggeen n AAttoommss MMaasss s RRaattiioo

N

Nuummbbeer r MMaasss s ((aammuu)) NNuummbbeer r MMaasss s ((aammuu)) MMaasss s ccaarrbboon n / / MMaasss s hhyyddrrooggeenn

12 12 11 1 12 2 aammuu = = 1122 1 1 amu amu 11 24 24 [2 x 12] [2 x 12] 2 2 [2 x 1] [2 x 1] 2 24 4 aammuu = = 1122 2 2 amu amu 11 120 120 [10 x 12] [10 x 12] 10 10 [10 x 1] [10 x 1] 1 1220 0 aammuu = = 1122 10 10 amu amu 11 600 600 [50 x 12] [50 x 12] 50 50 [50 x 1] [50 x 1] 6 6000 0 aammuu = = 1122 50 50 amu amu 11 (6.02 x 10

(6.02 x 102323_{) x (12)}_{) x (12)} Avogadro’sAvogadro’s_number_number _{(6.02 x 10}_{(6.02 x 10}₂₃₂₃_{) x (1)}_{) x (1)}

(6.02 x 10 (6.02 x 102323₎_{) x}_{x ((1}₁₂_{2)) =}_{= 1}₁₂₂ (6.02 x 10 (6.02 x 102323₎_{) x}_{x (1)}₍₁₎ ₁₁ Avogadro’s Avogadro’s number number Avogadr Avogadr oPaper oPaper

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Amadeo

Avogadro

(1776 (1776 – – 1856)1856)

1 mole = 602213673600000000000000

or

or 6.022

6.022 x

x 10

10

23

thousands thousands millions millions billions billions trillions trillions quadrillions quadrillions ? ? There is Avog

There is Avogadro's number of particles adro's number of particles in a mole of in a mole of any substance.any substance.

Particles in a Mole

Amedeo Avogadro

Amedeo Avogadro(1766-1856)(1766-1856)

never knew his own number;

it was named in his honor by a

French scientist in 1909.

its value was first estimated

by Josef Loschmidt, an Austrian

chemistry teacher, in 1895

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Careers in Chemistry

-Philosopher

Philosopher

Q:

Q: How much is a mole?How much is a mole? A:

A: A m A mole is a quantity uole is a quantity used by chemists sed by chemists to count to count atoms andatoms and molecules.

molecules. A mA mole of something ole of something is equal to 6.02 is equal to 6.02 x 10 x 10 2323 _{“somethings.”}_{“somethings.”}

1 1 mole

mole =

= 602

602 200

200 000

000 000

000

Q:

Q: Can you give me an example to put that number in perspective?Can you give me an example to put that number in perspective? A:

A: A com A computer that can puter that can count 10,000,000 count 10,000,000 atoms per second atoms per second would would take 2,000,000,000 years to count 1 mole of

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Counting to 1 Mole

Is that right?

Is that right? A c A computer counting omputer counting 10 million atoms 10 million atoms every second every second would need to count for 2 billion years to count just a single mole

would need to count for 2 billion years to count just a single mole..

Lets look at the

Lets look at the mathematics.mathematics.

Therefore 1 year has 31,536,000 seconds or 3.1536 x 10

Therefore 1 year has 31,536,000 seconds or 3.1536 x 1077 _sec._sec. A

A computer counting 10,000,00computer counting 10,000,000 atoms every 0 atoms every second could countsecond could count 3.153 x 10

3.153 x 101414 _{atoms every year.}_{atoms every year.} Finally, 6.02 x 10

Finally, 6.02 x 102323 _{atoms divided by 3.1536 x 10}_{atoms divided by 3.1536 x 10}1414 _{atoms every year}_{atoms every year} equals

equals 1,908,929,477 years1,908,929,477 years or approximately 2 billion years!or approximately 2 billion years! x sec = 1 year

x sec = 1 year 365 days365 days 1

1 yyeeaarr 1 1 ddaayy 2 24 4 hhoouurrss 660 0 mmiinn 1 hour 1 hour 60 sec 60 sec 1 min

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How Big is a Mole?

One mole of marbles would

One mole of marbles would cover the entire Earth

cover the entire Earth

(oceans included

(oceans included) for

) for a depth of three

a depth of three miles.

miles.

One mole of $100 bills stacked one on top of another

would reach from the Sun to Pluto and back 7.5 million

times.

It would take light 9500 years

It would take light 9500 years to travel from the

to travel from the

bottom to the top of a stack of 1 mole of $1 bills.

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A

Avogadro’

vogadro’s Number

s Number



 A A MOLEMOLE of any substance contains as many elementary unitsof any substance contains as many elementary units (atoms and molecules) as the number of atoms in 12 g of the (atoms and molecules) as the number of atoms in 12 g of the isotope of carbon-12.

isotope of carbon-12.



 This number is called This number is called AAVOGADRO’s number VOGADRO’s number NN_A_A == 6.02 x 106.02 x 102323

particles/mol particles/mol



 The mass of one mole of a substance is called MOLAR MASSThe mass of one mole of a substance is called MOLAR MASS symbolized by MM

symbolized by MM



 Units of MM are g/molUnits of MM are g/mol

  ExamplesExamples H H₂₂ hhyyddrrooggeenn 22..002 2 gg//mmooll H Hee hheelliiuumm 44..0 0 gg//mmooll N N₂₂ nniittrrooggeenn 2288..0 0 gg//mmooll O O₂₂ ooxxyyggeenn 3322..0 0 gg//mmooll CO CO₂₂ ccaarrbboon n ddiiooxxiiddee 4444..0 0 gg//mmooll

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