THE MOLE IN CHEMISTRY

Mona Lisa, Leonardo da Vinci, 1504. Italian.

Vocabulary:

• Mole
• Avogadro’s number
• Particle:
• Atom
• Molecule
• Formula unit

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BUT FIRST, SCIENTIFIC NOTATION REVIEW

Scientific Notation: A way to represent very large numbers and very small numbers using powers of 10.

Example: 4,500,000

The four is in the millions place.

One million is 1,000,000 which is 10⁶

So 4,500,000 is the same as 4.5 x 10⁶

Practically speaking, we moved the decimal over 6 spaces to the left and multiplied by 10⁶

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

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31,000,000,000 =

8900 =

45,000. =

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

​

31,000,000,000 = 3.1x10¹⁰

8900 =

45,000. =

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

​

31,000,000,000 = 3.1x10¹⁰

8900 = 8.9x10³

45,000. =

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

​

31,000,000,000 = 3.1x10¹⁰

8900 = 8.9x10³

45,000. = 4.5000x10⁴

BUT FIRST, SCIENTIFIC NOTATION REVIEW

What about really small numbers?

Example: 0.0000045

The four is in the millionths place.

One millionth is 0.000001 which is 10^-6

So 0.0000045 is the same as 4.5 x 10^-6

Practically speaking, we moved the decimal over 6 spaces to the right and multiplied by 10^-6

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

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0.00072 =

0.0000000801 =

0.0000300 =

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

​

0.00072 = 7.2x10^-4

0.0000000801 =

0.0000300 =

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

​

0.00072 = 7.2x10^-4

0.0000000801 = 8.01x10^-8

0.0000300 =

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Try converting these numbers to scientific notation:

​

0.00072 = 7.2x10^-4

0.0000000801 = 8.01x10^-8

0.0000300 = 3.00x10^-5

BUT FIRST, SCIENTIFIC NOTATION REVIEW

Let’s do a little scientific notation math:

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7.2x10⁴ / 6.2x10⁵ =

Do this on your calculator however you know how to.

Did you do this?

(7.2x10^4) / (6.2x10^5) = 0.12

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BUT FIRST, SCIENTIFIC NOTATION REVIEW

Let’s do a little scientific notation math:

​

7.2x10⁴ / 6.2x10⁵ =

​

Here is the proper (and easier) way to do it on your calculator:

7.2EE4 / 6.2EE5 = 0.12

(no parentheses, no x sign, no 10^)

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BUT FIRST, SCIENTIFIC NOTATION REVIEW

Let’s do a little scientific notation math:

​

1.15x10^-4 / 8.92x10⁷ =

​

On your calculator:

1.15EE-4 / 8.92EE7 =

= 1.28x10^-12

SO NOW, MOLES!

What is a mole?

MOLES!

Yes…but that’s not what we’re talking about here.

In chemistry, a mole is a quantity of something, just like the dozen is a quantity of something.

WHAT ARE SOME WORDS THAT MEAN A CERTAIN NUMBER OF SOMETHING?

MOLES!

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1 mole of anything = 6.02x10²³ of that thing

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(In the same way that

1 dozen of anything = 12 of that thing)

1 mol = 6.02 x 10²³ particles

MOLES!

So 1 mole of donuts =

602,000,000,000,000,000,000,000 donuts

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This number (6.02x10²³) is called Avogadro’s number.

WHERE DID THE MOLE COME FROM?

• The mole is defined as the number of atoms in 12 grams of pure carbon-12, the isotope of carbon with an atomic weight of 12.
• This corresponds to a value of 6.02214179×10²³ representative particles (e.g., atoms, molecules, formula units, ions, etc.) of the substance.
• A mole of any substance is the amount of that substance that contains 6.02213179x10²³ representative particles of that substance.

LET’S GET SOME PERSPECTIVE ON POWERS OF 10:

http://www.powersof10.com/index.php?mod=watch_powersof10

MOLES!

Here’s some more perspective:

National Debt: 27,800,000,000,000 dollars

Dist to sun: 5,702,400,000,000 inches

Stars in galaxy: 400,000,000,000 stars

Cells in body: 25,000,000,000,000 cells

1 mole: 602,000,000,000,000,000,000,000 units

MOLES!

More perspective:

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In order for us to count out Avogadro’s Number of anything, we would need all of the people of earth (7 billion) to count one item every second for 2.7 million years.

MOLES!

More perspective:

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One mole of small marshmallows would cover the United States of America to a depth of around 39 miles.

MOLES!

More perspective:

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A mole of rice grains would cover all the land area of the world to a depth of 246 ft.

MOLES!

More perspective:

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A mole of hockey pucks would be equal to the mass of the moon.

MOLES!

More perspective:

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A mole of baseballs would just about fit perfectly into a bag the size of the earth.

MOLES!

More perspective:

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In order to fit a mole of raindrops into a 100-ft diameter tank, the sides of the tank would have to be 280 higher than the distance from the earth to the sun.

MOLES!

More perspective:

• If one mole of pennies was divided equally between every person on earth (7 billion people), each person would receive 8.6 x 10¹³ pennies ($860 billion dollars.)
• Personal spending at the rate of one million dollars a day would use up each person’s wealth in 2356 years.
• Life would not be comfortable though. The surface of the planet would be buried in copper coins to a depth of about 425 meters.

MOLES!

Let’s try one on your own:

How tall in miles would 1.0 mole of pennies be?

• Experimentally determine the height of 15 pennies and use that measurement as a conversion factor. (e.g., 15 pennies = x cm)

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• Helpful conversion factors:

12 in = 1 ft 5280 ft = 1 mile 2.54 cm = 1.00 in

MOLES!

So what volume of water would contain 1 mole of water molecules?

MOLES!

Just 18 mL of water. That’s not much.

This much.

LET’S PRACTICE:

How many donuts would be in 13.5 dozen donuts?

13.5 dozen donuts

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12 donuts

1 dozen donuts

x

​

=

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162 donuts

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Start with given amount you are trying to convert.

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Use appropriate conversion factor.

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Write answer with units and rounded to proper sig figs.

LET’S PRACTICE:

How many donuts would be in 13.5 moles of donuts?

Remember:

1 mol = 6.02x10²³ particles

13.5 moles donuts

​

6.02x10²³ donuts

1 mole donuts

x

=

​

8.13x10²⁴ donuts

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Start with given amount you are trying to convert.

​

Use appropriate conversion factor.

​

Write answer with units and rounded to proper sig figs.

LET’S PRACTICE:

How many moles of copper would contain 3.62x10²² atoms of copper?

Remember:

1 mol = 6.02x10²³ particles (atoms, molecules, f.u.)

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3.62x10²² atoms Cu

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1 mole Cu

6.02x10²³ atoms Cu

​

x

=

​

0.0601 mol Cu

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Start with given amount you are trying to convert.

​

Use appropriate conversion factor.

​

Write answer with units and rounded to proper sig figs.

NOTICE!!

In the last example, I used the word “atoms” in reference to particles of copper because copper is an element and the smallest particle of an element is an atom.

If we are working with the particles of a compound, we would use the word “molecules” for a molecular compound or “formula units” for an ionic compound.

Let’s practice:

How many molecules of CO₂ would be in a 12.82 mole sample of CO₂?

Remember:

1 mol = 6.02x10²³ particles

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12.82 mol CO₂

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6.02x10²³ molec CO₂

1 mol CO₂

x

=

​

7.718x10²⁴ molecules CO₂

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Start with given amount you are trying to convert.

​

Use appropriate conversion factor.

​

Write answer with units and rounded to proper sig figs.

Try this:

How many moles of CuSO₄ would contain 9.12x10²² formula units of CuSO₄?

Remember:

1 mol = 6.02x10²³ particles (atoms, molecules, f.u.)

9.12x10²² f.u. CuSO₄

1 mol CuSO₄

6.02x10²³ fu CuSO₄

x

=

​

0.151 mol CuSO₄

Start with given amount you are trying to convert.

​

Use appropriate conversion factor.

​

Write answer with units and rounded to proper sig figs.

TIME TO PRACTICE ON YOUR OWN