The molar mass of oxygen gas (o2) is 32.00 g/mol. the molar mass of c3h8 is 44.1 g/mol.
what mass of o2, in grams, is required to completely react with 0.025 g c3h8?
0.018
0.034
0.045
0.091

the balanced chemical equation for the reaction is as follows;
 C₃H₈ + 5O₂ ---> 3CO₂ + 4H₂O
                   
stoichiometry of  C₃H₈ to O₂ is 1:5
   
number of moles of  C₃H₈ reacted - 0.025 g / 44.1 g/mol = 0.000567 mol according to molar ratio of 1:5
number of O₂ moles required are 5 times the amount of  C₃H₈ moles reacted therefore number of O₂ moles required - 0.000567 x 5 = 0.00284 mol .
mass of O₂ required - 0.00284 mol x 32.00 g/mol = 0.091 mol .
 answer is 0.091 mol