Moles. Mole: A)A small blind burrowing furry rodent B)A spy C)A skin condition D)6.02 x 10 23.

Mole:

A) A small blind burrowing furry rodent

B) A spy

C) A skin condition

D) 6.02 x 10 23

6.02 x 10 23

is called Avogadro’s Number

and a Mole

This is COLLECTIVE NOUN

What is the collective noun name for 12?

A dozen

Working with collective nouns

• A Dozen is easy to work with because the number 12 is a small number.

• Two dozen = 2 x 12 = 24• A half dozen = 12/2 = 6• 163.67 dozen = ????• 163.67 x 12 = 1964.04 (lots of eggs, or donuts or whatever…!)

Working with collective nouns

• A Mole is easy to work with because the number 6.02 x 10 23 is a number.

• Two moles = 2 x (6.02 x 10 23 )= 12.04 x 1023

• A half mole = (6.02 x 10 23 )/2 = 3.01 x 1023

• 163.67 moles = ????• 163.67 x (6.02 x 10 23 ) = 985.3 x 1023

(lots and lots of eggs, or donuts or whatever…!)

Review: Working with exponents

2 x (6.02 x 10 23 )= 12.04 x 1023

= 1.204 x 1024

163.67 x (6.02 x 10 23 ) = 985.3 x 1023

= 9.853 x 1025

Where did the Mole come from?

A Mole is defined as the number of atoms of Carbon in 12.000 grams of carbon.

(did somebody really count these out?)

Why 12 grams of Carbon?

Remember: The amu is based on Carbon-12

One carbon atom has a mass of 12 amu

But who can work with one carbon atom???

Why 12 grams of Carbon?

It just so happens that…

One carbon atom has a mass of 12 amu

One MOLE of carbons atoms has a mass of 12 grams

Grams are easy to work with !

But this magic doesn’t just work for Carbon!

The atomic mass (in grams) of any atom is the mass of one MOLE of that element

The gram formula mass of any compound is the mass of one MOLE of that compound

Since chemists are unbelievably lazy….

MOLE

is often abbreviated as

MOL

Moles and GFM

Since the gram formula mass is the mass of one mole, we can write this mathematically as:

GFM = grams per mole

= grams/mole

= grams

mole

Moles and GFM

So, for Na, with a GFM of 23 g

There are 23 grams per mole of Na = 23 grams/mole

= 23 grams mole

Moles and GFM

So, for NaCl, with a GFM of 58 g

There are 58 grams per mole of NaCl = 58 grams/mole

= 58 grams mole

Converting grams to Moles

This formula is in Table T;

# of moles = given mass gram formula mass

Converting grams to Moles

# of moles = given mass gram formula mass

How many moles of Na are in 333 g of Na?

# of moles = 333g 23g/mole

# of moles = 14.48 g/g/mole = 14.48 moles

You try it!

How many moles are there in 678 grams of NaCl?

# of moles = 678 grams GFM

GFM of NaCl = 23 + 35.5 = 58.5g/mol

# of moles = 678 grams NaCl 58.5 g/mol

= 11.6 mole NaCl

Converting Moles to Grams

This formula is NOT in Table T, but you can get it by rearranging the grams to mole formula

Grams = # of moles x GFM

Grams = # of moles x grams

mole

Converting Moles to Grams


How many grams are there in 6.37 moles of Na?

Grams = 6.37 moles x 23 grams Na moleGrams = 147 grams Na

You try it!


How many grams are there in 106.8 moles of NaCl?

Grams = 106.8 moles x 58.5 grams/mol = 6248 grams NaCl

Mole Relationships in chemical equations

A recipe calls for:

2 cups flour

4 eggs

1/2 cup chocolate chips

To make double the amount:

4 cups flour

8 eggs

1 cup chocolate chips

Mole Relationships in chemical equations

A recipe calls for:

2 cups flour

4 eggs


To make half the amount:

1 cups flour

2 eggs


You can write this as a chemical reaction (all cooking is!)

2 cups flour + 4 eggs + ½ cup chips 1 cake

2 4 .5 1

These numbers show the RATIOS of ingredients in the recipe that make it come out right

If you know the correct ratios, you can double, triple or halve the recipe easily.


2 4 .5 1

Suppose you only have 3 eggs ? How much flour will you need?

4 eggs (original recipe)3 eggs (new recipe)

= 2 cups flour (original recipe) X cups flour (new recipe)

Cross multiply and solve for x

4X = 2x3 X = 6 4

X = 1.5 cups flour


2 4 .5 1

Suppose you only have 3 eggs ? How many cups of chips will you need?


= .5 cups chips (original recipe) X cups chips (new recipe)


4X = .5 x 3 X = 1.5 4

X = .375 cups chips


2 4 .5 1

Suppose you only have 3 eggs ? How many cakes can you make?


= 1 cake (original recipe) X cakes (new recipe)


4X = 1 x 3 X = 3 4

X = .75 cakes

In balanced chemical equations..

the coefficients in front of the formulas can be interpreted two ways:

as numbers of molecules (easy to visualize)Or

As number of moles (practical in the lab)

4 NH3 + 5O2 4NO + 6H2O

2 C2H6 + 7 O2 4 CO2 + 6 H2O

2 7 4 6 (original)

How many moles of water will be produced if 3 moles of ethane are burned?

3 ? ? X (new)

2 moles ethane (original)3 moles ethane (new)

= 6 moles water (original)X moles water (new)

2X = 3 x 6 X = 18/2 X = 9 moles water

You try: How many moles of carbon dioxide will be produced? How many moles of oxygen gas will be needed?

Moles. Mole: A)A small blind burrowing furry rodent B)A spy C)A skin condition D)6.02 x 10 23.

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