. How many grams of oxygen are required to burn 47.0g of C3H8?

Answer 1

how many moles in 47g of C3H8?
what is the reaction equation? That will tell you how many moles of O2 to use.
convert that back to grams.

Answer 2

C3H8 + 5O2 ==> 3CO2 + 4H2O is the equation you need.