1. Avogadro’s Hypothesis
-The mole is a number like a dozen is a number or a
week is a number of days (usually as measurement
units)
-The mole was established by using the number of atoms in 12 grams of carbon-12.

2. Avogadro’s Hypothesis
-The number of particles in one mole is 6.02 × 1023 (FYI, this is a very large number)
602,350,000,000,000,000,000,000
-6.02 × 1023 is also called Avogadro’s number
-At standard temperature (0°C) and pressure (1 atm) (STP), 22.4 liters of any gas will ALWAYS contain 6.02 × 1023 particles

3. Avogadro’s Hypothesis(

4. Avogadro’s Hypothesis
To solve problems:
DON’T FORGET UNITS!
If you want # of atoms/molecules:
-Take the number of moles and multiply it by
6.02 × 1023
ex: How many molecules are in 1 mole of O2?
1 mole × 6.02 × 1023 = 6.02 × 1023 molecules of O2
If you want # of moles:
-Take the number of molecules/atoms and divide it by 6.02 × 1023
ex: How many moles are in 6.02 × 1023 molecules of
O2?
6.02 × 1023 molecules ÷ 6.02 × 1023 = 1 mole of O2

5. Avogadro’s # Problems Answer the following questions:
How many molecules are in 3.00 moles of CO2?
How many molecules are in moles of H2O?
How many atoms are in 1.50 moles of He?
How many moles are in × 1023 molecules of H2?
How many moles are in 6.02 × 1023 atoms of Mg?
How many moles are in 2.00 × 1023 particles of NaCl?