Percent Composition, Moles, Molecules, and Atoms

                                                                                                                                                            GIA 5-7
Learning Objective:                                                                                                                           Chapter 10

• Determine percent composition by mass of one element in a compound. 

• Determine the mass of one element in a compound from percent composition data.  

• Determine the number of atoms of one element from percent composition data. 

Working Mode:  Pairs

Keywords:  Molar Mass, Mole, Atom, Molecule, Avogadro’s Number, Percent Composition by Mass

Instructions:  Use the information given to answer each question.  

A pure sample of lithium carbonate (Li₂CO₃) was found to have a mass of 24.0 grams.  The molar mass of lithium carbonate is 73.89 gram/mole.  The molar mass of oxygen is 16.00 gram/mole.  The molar mass of lithium is 6.94 gram/mole.  Avogadro’s Number is 6.02 x 10²³. 

Student 1:  Calculate the percent composition by mass of lithium in the sample.

Student 2:  Calculate the mass of oxygen in the sample. 

Student 1:  Calculate the moles of carbon in the sample. 

Student 2:  Calculate the number of lithium atoms in the sample.