This link has been bookmarked by 11 people . It was first bookmarked on 05 Aug 2006, by Mark.
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30 Sep 16
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electrolysis can be (and is) performed at very high efficiencies close to 100%.
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If you use a battery, then chances are that the battery was charged with electricity produced by burning fossil fuels, so that the hydrogen you produce isn't produced cleanly. If you use a solar cell, however, then the hydrogen will be produced cleanly, except for any pollutants that were emitted when the cell was made (we say that the solar cell has no "point-of-use" emissions).
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If you use a battery or solar panel that generates less than 1.5 volts, then it will be necessary to add an electrolyte, such as a salt, acid, or base, that will disassociate into charged ions and increase the flow of electrical current.
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If the electrodes are made of metal, and if there is another metal dissolved into the water, then the metal electrode will become plated with the dissolved metal. This process is called electroplating, and is used in industry to produce aluminum and also to plate things with gold or silver.
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- Now calculate the theoretical (maximum) volume of the hydrogen produced, also in cubic meters, from the other data for the current and the time, using "Faraday's First Law":
Vtheoretical = (R I T t) / (F p z),
where R=8.314 Joule/(mol Kelvin), I = current in amps, T is the temperature in Kelvins (273 + Celsius temperature), t = time in seconds, F = Faraday's constant = 96485 Coulombs per mol, p = ambient pressure = about 1 x 105 pascals (one pascal = 1 Joule/meter3), z = number of "excess" electrons = 2 (for hydrogen, H2), 4 (if you're measuring oxygen production instead).
- Finally, calculate the efficiency by comparing the volume produced to the theoretical maximum volume:
Efficiency (in %) = 100 x Vproduced / Vtheoretical .
- Now calculate the theoretical (maximum) volume of the hydrogen produced, also in cubic meters, from the other data for the current and the time, using "Faraday's First Law":
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- Discuss the possible sources of inefficiencies/errors, such as
- Failure to capture all the hydrogen
- Energy lost to heat
- Various measurement errors
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electrical pressure to push electrons into the water at this end.
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It is true that hydrogen is a very explosive fuel, but so is natural gas and gasoline
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29 Aug 11
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The process by which we generate hydrogen (and oxygen) from water is called electrolysis.
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The process by which we generate hydrogen (and oxygen) from water is called electrolysis
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If you use a solar cell, however, then the hydrogen will be produced cleanly, except for any pollutants that were emitted when the cell was made (we say that the solar cell has no "point-of-use" emissions).
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electrolyte
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electroplating
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ammeter
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energy (electricity) + 2 H2O -> O2 + 2 H2 .
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Some people are worried that hydrogen might be too dangerous. It is true that hydrogen is a very explosive fuel, but so is natural gas and gasoline
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08 Jul 11
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03 Mar 11
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16 Feb 09
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24 Jun 08
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23 Jun 08
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25 Mar 08
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05 Aug 06
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