According to the question-
1 mol C3H8O = 60.096 g C3H8O
2 mol C3H8O = 9 mol O2
1 mol O2 = 31.998 g O2
[(3.00 g C3H8O)/1][(1 mol C3H8O)/(60.096)][(9 mol O2)/(2 mol C3H8O)][(32.998 g O2)/(1 mol O2)] = 7.1880435 g O2
Since 7.1880435 g of O2 is needed, and 7.38 g of O2 is available, 0.199565 g of O2 will be left over and oxygen is present in excess.
Next, we need to convert 0.199565 g of O2 into moles of O2:
[(0.199565 g O2)/1][(1 mol O2)/(31.998 g O2)] = 0.005999 mol O2, or 0.006 mol O2