Coke is an impure form of carbon that is often used in industrial preparations of metals from their oxides. A 7.20 x 104 g sample of coke is reacted with copper(II) oxide. Only the carbon present in the coke reacts with the CuO producing 7.25 x 105 g of copper by the following reaction. What is the mass percentage of carbon in the impure coke?
2CuO + C ---> 2Cu + CO2