Please help with some basic Product Yield questions!!! (Chemistry)

Consider Na + O2---------> Na2O

1st Balance...then
Given 64g of O2, how many grams of Na2O can be created?

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Consider:
Ca3N2 + Pb ---------> Ca + Pb3N4

1st balance, then...
Given 64g of Ca3N2, how many grams of Pb3N4 can be created?

Balanced equation:
4Na + O2 → 2Na2O
1mol O2 will produce 2 mol Na2O
Molar mass O2 = 32g/mol
64g O2 = 64/32 = 2 mol O2
From the equation , this will produce 4 mol Na2O
Molar mass Na2O = 23*2 + 16 = 62g/mol
4mol Na2O = 4*62 = 248g Na2O produced.

Balanced equation:
2 Ca3N2 + 3 Pb = 6 Ca + Pb3N4
2mol Ca3N2 will produce 1 mol Pb3N4
Molar mass Ca3N2 = 148.25 g/mol
64g Ca3N2 = 64/148.25 = 0.432 mol
This will produce 0.432/2 = 0.216 mol Pb3N4
Molar mass Pb3N4 = 677.7 g/mol
0.216 mol = 0.216*677.7 = 146.4g Pb3N4

The answer should have 2 sig figs :
Answer = 1.5*10^2g Pb3N4 produced.

It's just conversions and stochiometry, just keep in mind that not all 64g of O2 are going to be used because its in excess. Same goes with the second one. I'd tell you exactly how to do it but just think about it, you can do it :) that's how you truly learn :)