9.2 Warm Up:

–Give the oxidation numbers for the following compounds1. NaPO4

2. HClO3

3. C6H12O6

Calculations with Chemical Formulas1. Formula Mass (Molar Mass)

• sum of the atomic masses of all atoms represented in its formula

• label for formula mass is atomic mass units (amu)

• Determine the formula mass for the following compounds.

(a) CO2

(b) Mg(C2H3O2)2

2. Percentage Composition

• To find the mass percentage of an element in a compound, the following equation can be used.

• The mass percentage of an element in a compound is the same regardless of the sample’s size.

• Percent Composition from the Chemical Formula Calculate the percent composition of each

element in the following compounds.(a) C in CO2

(b) O in Mg(C2H3O2)2

• Percent Composition from Mass Data When a 13.60 gram sample of magnesium

oxide is decomposed, 5.40 g of oxygen is obtained. What is the percentage composition of each element in this compound?

Wrapping It Up• Reflect on what you have learned concerning the today’s

topic.

• Respond to the following…– What are the three most important things you learned

today?– What is one question you would still like answered?– What is the one way what you have learned connects with

what you knew before?