Unit 3 Chemical Quantities

The MOLE

A. What is a mole?

1. Chemistry is a quantitative science. What does this term mean?

Gives answers in numerical form

(tells exactly how much)

Compare that with qualitative informationqualitative information which describes, and is less exact – “bigger”, “smaller”, “more”, “less”, “heavier”, “lighter”. etc

A. What is a mole?

2. How do we measure quantities of matter?

a. By counting –examples: apples, eggs, donuts

b. By weighing –examples: bulk candy, meats by the pound, peanut butter by 16oz. Jars

c. By volume –examples: gallon of milk, quart of orange juice, 2-liter of pop

A. What is a mole?

3. Some of the units we use to indicate specific numbers:

a. Pair – 2

b. Dozen – 12

c. Gross – 144

d. Ream - 500

A. What is a mole?

4. The mole is just like this.

Define “mole”:

A unit that represents 6.02 X1023 representative particles

B. The number of particles in a mole.

1. Counting atoms, ions, molecules, and formula units is impractical because they’re too small!

B. The number of particles in a mole.

2. We use a counting unit (”the mole”) to count these representative particles.

B. The number of particles in a mole.

3. How many “representative particles” are contained in 1 mole?

6.02 X1023 representative particles Atoms, molecules, formula units, ions,

etc

B. The number of particles in a mole.

4. This is an experimentally-determined number. It is called _Avagadro’s__ __number_, in honor of this Italian scientist.

Sample Calculations

Using Dimensional Analysis, please solve the 2 sets of calculations. It is very important that you show your work, and the units, in your work and in the final answer.

Begin by working with a neighbor, then we’ll do them together.

Sample Calculations

1. How many moles of magnesium is 1.25 X1023 atoms of magnesium?

Given

The Mass of One MOLE of … (anything)

• “Atomic mass” – the mass of one atom

• “Formula mass” – the mass of a formula unit (an ionic compound)

• “Molecular mass” – the mass of a molecule (molecular compound)

C. The Mass of a Mole of an Element

1. Define “gram atomic mass” – the amount of element needed to weigh out exactly one mole of atoms of that element

a. What is the gram atomic mass of carbon? 12 grams

b. What is the gram atomic mass of Hydrogen? 1.00 grams

c. What is the gram atomic mass of Sulfur? 32 grams

“gram atomic mass”

This is the amount of an element (in grams) needed to weigh out exactly one mole of atoms of that element. [6.02x1023 atoms]

D. The Mass of a Compound

1. Define gram molecular mass – the amount of a molecular compound needed to weigh out exactly one mole of molecules of that compound

a. What is the gmm of sulfur trioxide?

SO3

Sulfur = 1 atom X 32 = 32Oxygen = 3 atoms X 16 = 48

80 grams total

D. The Mass of a Compound

1. Define gram molecular mass – the amount of a molecular compound needed to weigh out exactly one mole of molecules of that compound.

b. What is the gmm of hydrogen?

Remember, Hydrogen is one of the diatomic molecules … H2

1.00 X 2 2.00 grams

D. The Mass of a Compound

1. Define gram molecular mass – the amount of a molecular compound needed to weigh out exactly one mole of molecules of that compound

c. What is the gmm of carbon dioxide?

CO2

Carbon = 12.00 X 1 = 12.00Oxygen = 15.999 X 2 = 31.998

43.998 grams

D. The Mass of a Compound

2. Define gram formula mass – the amount of an ionic compound needed to weigh out exactly one mole of formula units of that compound

a. What is the gfm of sodium chloride?NaClsodium = 22.989 X 1 = 22.989chlorine = 35.453 X 1 = 35.453

58.442 grams

D. The Mass of a Compound

2. Define gram formula mass – the amount of an ionic compound needed to weigh out exactly one mole of formula units of that compound

b. What is the gfm of ammonium carbonate? NH4

+ + CO3-2

(NH4)2CO3

Nitrogen = 14.007 X 2 = 28.014Hydrogen = 1.008 X 8 = 8.064Carbon = 12.01 X 1 = 12.01Oxygen = 15.999 X 3 = 47.997

96.085 grams

D. The Mass of a Compound

2.. Define gram formula mass – the amount of an ionic compound needed to weigh out exactly one mole of formula units of that compound

c. What is the gfm of potassium oxide?

K2O

K = 39.098 X 2 = 78.196

O = 15.99 X 1 = 15.99

94.186g

• Now more practice problems in your

Notepack!!!