Aim: What is the Mole?

Do Now: Answer should be in the correct number of significant figures.

1. 4.9 × 102 + 7.9 × 103 3. (1.247 × 10–3) ÷ (2.9 × 10–2)

2. 4.9 × 10-6 - 7.9 × 10-5 4. (2.6 × 105) (9.2 × 10–13)

Counting large numbers…• Easier when you use counting units:

Dozen

Ream

Pair

Gross

•Regardless of the object, the number that the units represents is always the same

•Atoms and molecules are extremely small, making it impossible actually count them (even in the smallest of samples)

•Chemists need a unit for counting accurately the # of atoms, molecules, or formula units; they use the mole

•Mole (mol) = the SI base unit used to measure the amount of a substance

•1 mole of anything contains 6.02 x 1023

representative particles

1 mole of apples =

6.02 x 1023 apples

1 mole of diamonds =

6.02 x 1023 diamonds

1 mole of baseballs =

6.02 x 1023 baseballs

1 mole of carbon atoms =

6.02 x 1023 carbon atoms

The same applies to moles of compounds

•How many molecules are in 1 mol NH3?

6.02 x 1023 NH3 molecules

•How many molecules are in 1 mol C9H8O4?

6.02 x 1023 C9H8O4 molecules

What is Avogadro’s Number

•6.02 X 1023 representative particles/mol

•1 mol of any substance has 6.02 X 1023 representative particles

What are representative particles?

•Representative particles refers to the species present in a substance: usually atoms, molecules, or formula units

Converting Particles to Moles

• How many roses are in 3 ½ dozen?

USE CONVERSION FACTORS!!!

3.5 dozen x 12 roses =42 roses

1 dozen conversion factor

• How many pencils are in 6 gross?

6 gross x 144 pencils =864 pencils

1 gross conversion factor

Conversion factor

•A conversion factor is used to convert a measured quantity to a different unit of measure without changing the relative amount. To accomplish this, a ratio (fraction) is established that equals one (1)

Converting Number of Particles to Mole

Conversion factor

Converting number of atoms to moles

Units you want are on top

These units cancel out

0.465

Converting Moles to Particles and Particles to Moles

•How many moles contain 4.50 x 1024 atoms of zinc?

4.50 x 1024 atoms Zn x 1 mol zinc

6.02 x 1023 atoms Zn

7.48 mol Zn

Solve

How many moles of magnesium is 1.25 X 1023 atoms of magnesium?

Converting moles to number of particles

Conversion factor

Converting Moles to Particles

How many atoms can be found in 3.91 moles of xenon?

Converting Moles to Particles

•How many particles of sucrose are in 3.50 moles of sucrose?

3.50 mol sucrose x 6.02 x 1023 rep. part.

1mol

2.11 x 1024 particles of sucrose

Solve

How many cadmium atoms are there in 6.57 × 103

moles?

• 2. How many molecules are in 2.00 moles of H2O?

Conv. Factor(s) Set-Up

• 3. How many atoms are in 2.00 moles of H2O?

Conv. Factor(s) Set-Up

• How many moles are in 6.02 x 1023 atoms of carbon?

Conv. Factor(s) Set-Up

• 10. If you have 0.00812 mole of H2CO3, how many molecules do you have?

Conv. Factor(s) Set-Up