Molar Mass----> Mass of the Atom

• The mass in grams of 1 mole of a substance is called a “Molar Mass”
• It can be determined from the atomic mass on the periodic table.
• Measured in g/mol.
• Some common masses are:

1. Hydrogen =1.0079
2. Helium = 4.0
3. Nitrogen = 14.01
4. Zinc = 65.37
5. Iron = 55.845
6. Sodium = 22.9
7. Uranium = 238.03

1) Molar Mass

• The atomic mass----> Molar Mass
• The molar mass is the weight of one mole or 6.02 x 1023 molecules.
• The base SI Unit for mass is the Kilogram.
• To determine the molar mass of a compound, add the mass of all the atom together.
• Always have 2 or more significant digits.
• For example: Find the Molar Mass of the compound CO2 (Carbon Dioxide)

1. Atomic mass carbon = 12.01      
2. Atomic mass of oxygen = 16.00
3. Molecular Mass for Carbon monoxide = the atomic mass carbon + the atomic mass oxygen
4. 12.01 + 2(16.00) = 44.01 g/mole

2) Moles to Volume Conversion:
Mass<-(Molar Mass)->Moles<-(Molar Volume)->Volume

• Volume at STP (Standard Temperature and Pressure)
• The Volume is always the same as long as it is the same STP.
• The Volume only applies to gases.
• 1 mole of any gas occupies the same volume.
• At 0 degrees celsius and 101.3 kPa (1 mol=22.4L) 
• 22.4L/mol is the molar volume at STP

• KEY information to remember:

1 mol = 6.02 x 1023 particles
1 mol = g-formula-mass (periodic table)
1 mol = 22.4 L for a gas at STP
 Examples:
1. A certain gas is found to occupy 0.040 moles at STP. Find the volume in liters.
(0.040 mol) x(22.4 L/ 1 mol) = 0.896L

2. How many moles of Sulfur atoms are present in 11.2 L of Sulfur gas at STP?
(11.2L)x(1mol/ 22.4L) = 0.5 mol