4.5 moles of oxygen reacting with enough sodium will form how many moles of sodium oxide? How do you solve?

Keep this procedure. It will come in handy working about 90 of the stoichiometry problems.

1. Write and balance the equation.
2Na + O2 ==> Na2O

2. Convert grams (usually given) to mols which is mols = grams/molar mass. In this case mols are given in the problem so this step isn't necessary.

3. Using the coefficients in the balanced equation, convert mols of what you have (in this case O2) to mols of what you want (in this case Na2O).
That is 4.5 mols O2 x (1 mols Na2O/1 mol O2) = 4.5 x 1/1 = 4.5 mols Na.