The Mole Notes - Juhl's Science



The Mole

Mole: The chemists counting unit, the number of particles in a substance.

Symbol: mol

Unit: mol

Atomic mass (atomic mass unit/ grams): the average of the atomic masses of all the isotopes of that element. Given on the Periodic Table

Molar mass (formula mass/ grams): The sum of the atomic masses of all the atoms in a molecule.

The number of grams you need to make one mole of atoms of an element is equal to the atomic mass of the element.

Avogadro’s number: the number of representative particles contained in one mole of a substance

- 1 pair = 2

- 1 dozen = 12

- 1 mole = 6.02x1023

Tally Marks

- For one minute see how many tally marks you can make.

- Who has the most

- How long would it take to write to 6.02x1023 tallies?

- 300 tallies in one minute.

o Hour?

o Days?

o Years?

|300 tally |60 min |24 hours |365 days |

|1 min |1 hour |1 day |1 year |

6.02 x 1023

Answer

1 mole = atomic mass (g) for an element

Molar mass (g) for a compound

1 mole ? grams

Al 26.98 g

Ba 137.33 g

Nitrogen gas 28 g

Sulfur dioxide 64.06

Cu 63.5 g

Mole Map

GAS (LITERS) ( MOLE ( FORMULA MASS (GRAMS)

(

# OF ATOMS/ELEMENTS/FORMULA

UNITS/ MOLECULES/ COMPOUNDS

Mole Ratios: In a compound, the number of atoms is in mole rations, H2O there are 2 moles of hydrogen and 1 mol of Oxygen

Completing the Math

Conversion factor is a ration of equivalent measurements used to invert a quantity from one unit to another, also known as T-charts.

1. Write down everything you know and want

2. Create a T-chart

|Given |Wanted ratio |

| |Standard known ratio |

Example 1: Calculate the amount of eggs in dozens in a box containing 432 eggs.

432 eggs

X dozen eggs

|432 eggs |1 dozen egg |36 dozen eggs |

| |12 eggs | |

Example 2: Find the amount of moles in a sample containing 3.01x1024 carbon atoms.

3.01 x 1024 C atoms

X mol C

|3.01 x 1024 C atoms |1 mol C |5 mol C |

| |6.02 x 1023 atoms | |

Mole to Grams and Back

Examples:

Example 1: Calculate the mass of 5 moles of CO2.

5 mols CO2

X grams CO2

|5 mols CO2 |44 g CO2 |220 g CO2 |

| |1 mol CO2 | |

Example 2: Calculate the number of molecules in 5 moles of CO2.

5 mols CO2

X formula units CO2

|5 mols CO2 |6.02 x 1023 formula units CO2 |3.01 x 1024 molecules CO2 |

| |1 mol CO2 | |

Example 3: Calculate the number of molecules in 25 g of CO2.

25 g CO2

X formula units CO2

|25 g CO2 |1 mol CO2 |6.02 x 1023 f.u. CO2 |3.42 x 1023 molecules |

| |44 g CO2 |1 mol CO2 | |

Example 4: Calculate the number of atoms in 25 g of CO2.

25 g CO2

X atoms CO2

|25 g CO2 |1 mol CO2 |6.02 x 1023 f.u. CO2 |3 atoms CO2 |3.42 x 1023 formula units |

| |44 g CO2 |1 mol CO2 |1 f.u. CO2 | |

Practice Problems:

1. How many moles are there in 35.5 g H2CO3? (0.572)

2. How many grams are there in 0.0151 moles of water? (0.272)

3. How many grams are there in 2.5 moles of sodium hydrogen carbonate? (209.9)

4. How many moles are there in 1559 g barium chloride? (7.49)

5. How many moles are in 44.8 g aluminum sulfate? (0.131)

6. How many moles are in 1.00 g NaCl? (0.0171)

7. How many formula units are there in 55 g CaCl2? (2.98x1023)

8. What is the mass of 4.5x1026 formula units of Na2O? (46,328)

9. How many molecules are in 12.5 g H2O? (1.25x1024)

10. How many molecules are in 345 g Zn(NO3)2? (9.87x1024)

-----------------------

22.4L

Multiply 6.02 x 1023

Divide

6.02 x 1023

Multiply mass

Divide mass

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