Given that 1mole of propane react with 5 moles of Oxygen.find the number of moles of Oxygen reacted with 2.2g of propane
2.2 g is how many mols propane? That's g/molar mass = 2.2/44 = 0.05 mols.
So if 1 mol C3H8 uses 5 mols O2, then
...0.05 mols C3H8 uses x mol O2.