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- A unit of measurement for counting atoms or molecules
- 1 Mole= 602 billion trillion
- 602,000,000,000,000,000,000,000
- 6.02 X 1023 (this is known as Avogadro’s number)

Amadeo Avogadro

- Avogradro’s number is named in honor of Amedeo Avogadro (1776 – 1856)
- He studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

What can the mole be used for?

- We can count anything using the mole
- Example:
- 1 mole of M & M’s would stretch from here to the sun and back 200 billion times
- * assuming m&m’s are 1 cm in diameter and the distance to the sun is 93 million miles

- Can you swim in1 mole of water?
- 1 mole of H2O= about 1/3 of a cup (18 mL)

- 1 mole of M & M’s would stretch from here to the sun and back 200 billion times

- Example:

So, why use the mole?

- It is helpful in counting a large number of items
- If the items are extremely small

A Mole of Particles= 6.02 x 1023 particles

A mole of particles

= 6.02 x 1023C atoms

=6.02 x 1023H2O molecules

= 6.02 x 1023NaCl formula unit

1 mole C

1 mole H2O

1 mole NaCl

Conversion Factors

* 1 mole = 6.02 x 1023particles

Note: Particles could refer to atoms, molecules, formula units

* 1 mole = molar mass (g) of compound being used

Conversions:

- MUST use dimensional analysis
- MUST use the molar mass if grams are used in the problem
- Be able to convert from
- Moles to atoms or molecules
- Moles to grams
- Grams to moles

Example 1:

- How many atoms are in 0.500 mole of Al?
- Setup your problem using dimensional analysis:
- * Multiply across and divide by the number at the bottom

6.02 x 10 23 atoms Al

0.500 mol Al

=

3.01 x 10 23atoms Al

1 mol Al

Example 2:

- How many moles of Sulfur (S) are in 1.8 x 10 24atoms of sulfur ?
- (Use dimensional analysis)
- * Multiply across and divide by the number at the bottom

1.8 x 10 24atoms S

1 molS

=

2.99 mol S

6.02 x 10 23atoms S

Practice Problems

- 1.) How many moles are in 5.22 x 10 24 atoms of H2O?
- 2.) How many molecules of NaOH are in 23 moles of NaOH?

How to calculate mass of Sodium hydroxide given moles.

- How many grams are in 2.34 moles of Sodium hydroxide?
- You will utilize the molar mass you calculated and use dimensional analysis.

Molar mass of NaOH

2.34 mol NaOH

40.00 grams NaOH

93.60 grams NaOH

=

1mol NaOH

Calculating molecules, atoms, and formula units given mass.

- How many molecules are in 42 grams of NaOH?
- Avogadro’s number: (6.02 x 1023 atoms, molecules or formula units )= 1 mole)

6.02 x 1023molecules NaOH

1 mole NaOH

42 grams NaOH

40.00 grams NaOH

1 mole NaOH

Molar mass of NaOH

=

6.32 x 10 23molecules NaOH

Practice Problems

1.) Determine the molar mass for Barium Hydroxide.

2.) How many moles are in 25.00g of barium hydroxide?

3.) How many grams are in 6.7 moles of barium hydroxide?

4.) How many formula units are in 35.00g of barium hydroxide?

5.) How many molecules are in 4.5 moles of barium hydroxide?

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