How many moles of CO2 will be made from 115.4 grams of C3H8?

Answer 1

Do you mean by combustion?
C3H8 + 5O2 ==> 3CO2 + 4H2O

mols C3H8 = grams/molar mass
Convert mols C3H8 to mols CO2 using the coefficients in the balanced equation.