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How much electric energy needs to be used, to get 2.5l of hydrogen, when T=298K, pressure 10^5Pa? Electrolysis happens at 5V, efficiency is 75%.

I am quite lost here. Not sure were to start. I tried finding the needed current by getting hydrogen to kg and then by comparing to 0.0104*10^-6kg/C (electrolysis). I get 21.6*10^3C.

Energy - E=21600*5*0.75=60.75*10^3J

Of course wrong.

Second try:

n(H)=PV/RT i get that hydrogen has 0.1mole=0.1g=100C to electrolyse it.

Then E=100*5*0.75=375J - WRONG

I am quite lost here. Not sure were to start. I tried finding the needed current by getting hydrogen to kg and then by comparing to 0.0104*10^-6kg/C (electrolysis). I get 21.6*10^3C.

Energy - E=21600*5*0.75=60.75*10^3J

Of course wrong.

Second try:

n(H)=PV/RT i get that hydrogen has 0.1mole=0.1g=100C to electrolyse it.

Then E=100*5*0.75=375J - WRONG

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