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Atomic Mass & Formula Mass
• Atomic Mass
• Formula mass – just what it says it is!
• Example:– Atomic mass of carbon: 12.01amu– Formula mass of carbon dioxide
• 1 carbon atom = 12.01amu x 1 atom = 12.01• 2 oxygen atoms = 16.00amu x 2 atoms = 32.00
• Total = 44.01 amu for 1 molecule of CO2
The Mole
• An experimentally-defined number that is equal to 6.022 x 1023 particles
• Called Avogadro’s number, after physicist Amedeo Avogadro– 600 million trillion particles
– Can be atoms, molecules, anything in a distinct unit
Molar Mass
• Quantity in grams that equals the atomic mass of the element or compound
• For example: What is the molar mass of carbon dioxide?
Formula mass = 44.01amu / molecule Molar mass = 44.01g / mole
Chemical Equations
• Textual representation of a reaction• Definitions: Reactant, Product, Coefficient,
State of Matter• To balance:
– 1. Write down reactants and products with correct subscripts
– 2. Add coefficients so that there are the same number of each atom on both sides of the equation
– “Least Common Multiples”
Try This!
• Iron ores such as Fe2O3 are smelted, by reaction with carbon, to form metallic iron and carbon dioxide.
• Can you write and balance the equation?
• Can you name the iron ore?
Try This!
• When propane gas, C3H8, burns in oxygen, it produces water and carbon dioxide. Write and balance the equation.
What Does This Mean?
2Fe2O3 + 3C 3CO2 + 4Fe
2H2(g) + O2(g) 2H2O(g)
• Coefficients are proportions of moles– 2 moles of iron (III) oxide react with 3
moles of carbon to yield 3 moles of carbon dioxide and 4 moles of iron
2 moles iron (III) oxide
4 moles iron
2 moles iron (III) oxide
3 moles carbon dioxide
3 moles carbon dioxide
3 moles carbon
Try This!
• Butane, a common fuel in lighters, burns according to the following equation.
C4H10 + O2 CO2 + H2O
• Balance the equation• How many moles of carbon dioxide
can I produce if I burn 4 moles of butane?
Mass Calculations
Try This!
• Write a balanced equation for the following reaction:
Aluminum sulfate and sodium hydroxide react to form sodium sulfate and
aluminum hydroxide.
• How many grams of sodium hydroxide are needed to form 18.7 grams of sodium sulfate?
• If I begin with 25.9g of aluminum sulfate, how many grams of aluminum hydroxide will form?
