Charles flew the balloon for fifteen miles and stayed in the air for a total flight time of 45 mins. the balloon was made of silk coated with a thin layer of natural rubber and had a diameter of 27ft. he generated the hydrogen gas needed to lift the balloon by mixing a large amount of iron with aqueous sulfuric acid. if he used 1000 lbs. of iron and excess sulfuric acid, how many liters of hydrogen gas were made?