the mole: not just a furry little animal€¦ · the mole: by mass calculating molecular weight of...

S. GreenAu

The mole: not just a furry little animal

A problem: sprinkles in a flask

There are 3 ways to answer the question,

“How many?” or “How much?”

by count

by mass

by volume

Ex: apples

There are 14 apples (count)

There are 3.5 pounds of apples (mass)

There is a bag of apples (volume)

The SI unit for amount is the mole

A mole is like a dozen.

It is a word that stands for a numerical value.

Examples of these types of words/phrases:

•dozen =

•baker’s dozen =

•ream =

•what else?

Answering “How much” by count

The mole: by count

The number of items in a mole of items is 6.02x1023

Therefore, a mole of iron atoms is 6.02x1023 iron atoms.

A mole of pencils is 6.02x1023 pencils. (Way too many to sharpen.)

A mole of chemistry students…(Way too much grading.)

A mole of pennies…(Now that’s something I wouldn’t mind!)

How big is a mole?

A mole of marbles…

Dimensional analysis is back!

Everyone stop groaning, please…

The mole: by count

Dimensional analysis can be used to convert moles into another

unit, like individual molecules.

The phrase to remember is

“There are 6.02 x 1023 molecules of X in 1 mole of X.”

X is a compound.

A dimensional analysis bracket can now relate moles of a substance

to the number of individual molecules.

There are…

How many moles of MgCl2 are 3.1 x 1023 molecules?

There are…

How many molecules of C6H12O6 are 4.00 moles of C6H12O6 ?

There are…

How many moles of CO2 are

4.00 x 1024 molecules of CO2?

So far:

moles molecules6.02 x 1023

There are 6.02 x 1023 molecules in 1 mole.

Molecules are made up of atoms.

We can expand our dimensional analysis to include atoms.

Use another “There are…” statement.

will be different for each compound:

There are 3 atoms in 1 molecule of CO2

There are 24 atoms in 1 molecule of C6H12O6

There are ? atoms in 1 molecule of calcium phosphate?

relationship between molec and atoms

molecules atoms#

There are # atoms in 1 molecule.

We can combine all this into one

flowchart…

All together:


atoms#



There are…

How many atoms are in

2.3 moles of CO2?

There are…

How many moles of CaCO3 can be

made from 6.5 x 1025 atoms?

All together: The mole (by count)


atoms#



Answering “How much” by mass

The mole: by mass

The number of grams in one mole of a substance is called its

molecular weight

I will always abbreviate “molecular weight” as MW

The mole: by mass

The phrase to remember is

“There are (MW) grams of X in 1 mole of X.”

The mole: by mass

Determining molecular weight of an atom is not hard, however, we

must all do it the same way.

Find the atom on the periodic table and round its atomic mass to

one decimal place.

Example: The molecular weight of carbon is 12.0g/mol

note the unit.

note the use of one decimal place.

The mole: by mass

What is the molecular weight of

mercury?

nitrogen?

calcium?

chlorine?

phosphorus?

silver?

The mole: by mass

Calculating molecular weight of compounds is not hard, however,

we must all do it the same way.

Multiply each atomic mass by the number of atoms in the substance

and add the values together.

Example: Find the molecular weight of carbon dioxide

Look up the individual masses; round each to one decimal place

If there is more than one atom of an element, multiply its mass by the

number of atoms.

Add the results together.

The mole: by mass

carbon dioxide: CO2

1 C (12.0g/mol) = 12.0g/mol

2 O (16.0g/mol) = 32.0g/mol

total = 44.0 g/mol = MW of CO2

Find the MW of calcium chloride.

Calculate the molecular weight of NaCl.

Calculate the molecular weight of (NH4)2CO3.

Calculate the molecular weight of Mg(CN)2.

Calculate the molecular weight of FeCl3.

relationship between mole and g

mole gramsMW

There are _MW grams in 1 mole.

There are…

How many grams are in

2.514 moles of CO2?

There are…

How many moles of Na2SO4 are

125.0 grams of Na2SO4?

All together, now:


atoms#

grams

MW




There are…

How many molecules of Ca(ClO3)2

are 15.0 grams of Ca(ClO3)2?

There are…

How many grams of (NH4)2CO3 can be

made from 3.21 x 1026 atoms?

Note: the number of DA brackets will

be equal to the total number of boxes

you are traveling…


atoms#

grams

MW




Answering “How much” by volume

The mole: by volume

One mole of any gas at STP occupies 22.4 L of space.

Only for gases!

What’s STP?

standard temperature and pressure (two things that affects the volume

of a gas!)

standard temperature for a gas: 0oC

standard pressure for a gas: 1 atmosphere (more on this later)

relationship between moles and L

mole Liters22.4

There are 22.4 L in 1 mole of a gas at STP.

There are…

How many Liters are

6.2 moles of CO2 at STP?

There are…

How many moles of SO3 occupy

13.8 L at STP?

Of course, it can all be used

together…


atoms#

grams

MW




There are 22.4 L in 1 mole of a gas at STP.

Liters 22.4

There are…

How many grams of N2O5 occupy

43.1 L at STP?

There are…

How many Liters of HCN gas can be made

from 4.8 x 1023 atoms at STP?

Time for practice

Line up….

A friendly competition with a chance to win a

fabulous prize.

The Mole Bowl

The rules 2 people at a time, beginning with those who know “less”

this will slow the competition down, giving everyone a fair chance and a chance to learn

Everyone works problems at their seats. Collected at the end.

Winner remains standing, chooses whether they want the SMARTBoard or the chalkboard.

You may ask to be re-inserted into the game at any time.

Remember, the goal is to become better at this…

No limits except time

Winner of the class plays me. The rest of the class designs the problem.

If you beat me (and it HAS been done before): a great prize

the mole: not just a furry little animal€¦ · the mole: by mass calculating molecular weight of...

Documents