Need guidance with Chemistry - energy related

[timsher]

Hey guys, I'm really lost on this question...could somebody please point me in the right direction?

The annual world use of liquid hydrocarbon fuels for transportation purposes currently generates about 10^17 kJ. If we could instead run our transportation system by oxidizing hydrogen gas to gaseous water, we would likely have to obtain the hydrogen by electrolyzing water. Suppose we made and stored enough hydrogen for 100 years by electrolyzing seawater. By how much would the level of the oceans decrease (in m)?

Thanks!

 

[baldywaldy]

I'm not entirely sure on how to work out the answer but this may point you in the right direction :

1st calculate the amount of energy the oxidation of one mole of hydrogen produces
2nd calculate how many moles of hydrogen would be needed to meet the demand of 10^17kJ
3rd calculate how much water would be required to meet the demand of that many moles of hydrogen
4th calculate the volume of water that is equivalent to then work out the decrease in the sea level