Question

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?

Answer 1

You are given O2 and C3H8, this is a combustion reaction. The chemical reaction is C3H8 + 10O2 à 3CO2 + 4H2O. You are also given the molar mass of O2 which is 32.00 g/mol and C3H8 which is 44.1 g/mol. You are required to find the mass of O2 in grams. Since you have the reaction, oe mole of C3H8 is required to completely react 10 moles of O2. So,  

0.025g C3H8(1 mol C3H8/44.1 g C3H8)(10 mol O2/1 mol C3H8)(32 g O2/1 mol O2) = 0.1802 g O2