Chapter 8Molecular & Formula

Masses

Atomic mass

• The atomic mass is the average mass of an atom.

When using atomic masses make sure to round to at least one decimal place.

What is the atomic mass of actinium (Ac)?

What is the atomic mass of hydrogen (H)?

What is the mass of hydrogen (H2)?

Determine the Molecular Mass of Vitamin AC20H30O

Determine the Molecular Mass of Vitamin AC20H30O

20 x 12.0 = 240.030 x 1.0 = 30.01 x 16.0 = 16.0 = 286.0 amu

Formula Mass

• The formula mass is the mass of an ionic compound.

• An ionic compound is formed from a combination of metals and nonmetals.

• Formulas masses are calculated the same as molecular masses.

Determine the Formula Mass of Calcium PhosphateCa3(PO4)2

Determine the Formula Mass of Calcium PhosphateCa3(PO4)2

3 x 40.1 = 120.32 x 31.0 = 62.08 x 16.0 = 128.0 = 310.3 amu

The Mole

The MoleThe Mole

• A counting unit• Similar to a dozen, except instead

of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000

• 6.02 X 1023 (in scientific notation)• This number is named in honor of

Amedeo Avogadro (1776 – 1856)Amedeo Avogadro (1776 – 1856), and is called Avogadro’s Number.

The Mole (mol)The Mole (mol)• 1 mole of cookies = 6.02 X 1023 cookies

• 1 mole of cars = 6.02 X 1023 cars

• 1 mole of Al atoms = 6.02 X 1023 atoms

How big is a mole?

• How many cents are in one mole of pennies?

How big is a mole?

• How many cents are in one mole of pennies?

6.02 x 1023¢

How big is a mole?

• How many dollars are in 6.02 x 1023¢?

How big is a mole?

• How many cents are in one mole of pennies?

= $6.02 x 1021

6.02 x 1023¢100¢$1

How big is a mole?• There are about 6.6 billion (6.6 x 109) people on earth.• If we divided the 1 mole of pennies ($6.02 x 1021)

equally among all the people on earth how many dollars would you have?

How big is a mole?• There are about 6.6 billion (6.6 x 109) people on earth.• If we divided the 1 mole of pennies ($6.02 x 1021)

equally among all the people on earth how many dollars would you have?

$6.02 x 1021

6.6 x 109 people = $9.1 x 1011/person

$910,000,000,000 = 910 billion dollars

How big is a mole?

• How many years would it take you to spend your 910 billion dollars if you spent $100,000 per day?

How big is a mole?

• How many years would it take you to spend your 910 billion dollars if you spent $100,000 per day?

$9.1 x 1011

$100,000day

365 daysyear

= 25,000 years

25,000 years agoNeanderthals died out about 25,000 years ago

Homework

• Finish Mole Worksheet “How Big is a Mole”.

• Molecular and Formula Mass Worksheet• Don’t forget to show your work on your

calculations.