**By: Robbie Schmauk,**

Alex Zhang,

Kelsey Henges,

and Megan Mershon

Alex Zhang,

Kelsey Henges,

and Megan Mershon

**Chapter 10: Chemical Quantities**

**-By Count**

-By Mass

-By Volume

-By Mass

-By Volume

The Mole (mol)

**Three Methods**

of Measuring a

Substance

of Measuring a

Substance

Mole - unit of measuring the amount of particles.

- SI unit for measuring a substance

Avagadro's Number - 6.02 x 10

- Mole contains Avagadro's Number of Representative Particles

Representative Particles Include:

- Atoms, Molecules, Formula Units, and Ions

Example Problem:

How many moles are 2.80 x 10 atoms of Silicon?

Atomic Mass in grams is the mass of a mole of an element

Molar Mass - the mass of a mole of an element (grams)

Molar Mass of a Compound - Find the molar mass of each element in the compound and them together.

- Use molar mass to convert between moles

and mass

Molar Mass

Mole to Volume Relationship

Avagadro's Hypothesis - equal volumes of gases at the same temperature and pressure contain an equal number of particles.

Standard Temperature and Pressure (STP) - a temperature of 0 C and pressure of 101.3kPa (1atm)

Molar Volume - at STP molar volume = 22.4L

- 6.02 x 10 representative particles and 1 mole occupies 22.4L (at STP)

Example Problem:

What is the volume of 4.30 moles of N at STP?

23

24

2.80 x 10

atoms of Si

6.02 x 10

atoms of Si

23

24

23

1 mol of Si

4.65 mols of Si

=

Example Problem:

How many grams are in 5.00 moles of SO ?

3

SO = 32.07 + (15.99 x 3) = 80.04

3

5.00 mols of SO

3

1 mol of SO

3

80.04 g of SO

3

=

400 g of Si

o

23

2

4.30 mols

of N

2

1 mol

of N

2

22.4L of N

2

=

96.3L of N

2

Percent Composition

Percent Composition - the amount of the elements in a compound

% mass = mass of element in 1 mol of compound x 100

molar mass of compound

2

3

2

Empirical Formula - lowest whole number ratio of the atoms in a compound

Ex: C H O

Molecular Formula - same as experimentally determined empirical formula, or a whole number multiple of its empirical formula

Ex: C H O

4

6

4

Example Problem:

Calculate Percent Composition of NH .

3

Molar Mass of NH = 14.01 + (1.01 x 3) = 17.04

3

% of Nitrogen:

14.01g

17.04g

x 100 = 82.21%

% of Hydrogen:

3.03g

17.04g

x 100 = 17.78%

Works Cited

Matta, Staley, Waterman, Wilbraham, Prentice Hall Chemistry

Real World Example:

Volume of a gas changes based on

change in temperature in pressure.

This is why STP is important:

Lower Temp.

Higher Temp.

Real World Example:

Percent Composition of

a T-Shirt:

Real World Example:

Counting the individual pieces of

candy would be time consuming,

so measuring the jar in ml would

be an easier unit to use.