lab #2 - protons and electrons to form water as a...

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1. Theoretical Threshold voltage of water = 1.229 V 2. Measured Threshold voltage of water = 1.442 V 3. P=(Avg. Voltage)(Avg. Current) and E= (P)(t) For the E of H 2 , E (H2) =(V (H2) )(h (H2) ) where h (H2) =12.7E6 J/m 3 In order to find the efficiency of a fuel cell, we will divide the energy used divided by the potential energy of H 2 , or E/E (H2) Volume H2 (mL) Voltage (V) Current (mA) Time (sec) 0 1.580 200 0 5 1.586 192 195 10 1.576 185 300 15 1.577 192 515 20 1.577 188 740 Avg. Voltage = 1.5792 V Avg. Current = 0.1914 A P= (1.5792 V)(191.4 A) = .30226 W E= (.30226 W)(740 sec) = 223.672 W x sec E H2 = (.020 L)(12.7E6 J/m 3 ) =254.000 W x sec Effic. = (223.672 J)/(254 J) = .881 = 88.1% efficient 4. At the anode, hydrogen gas is decomposed into electrons and protons. The electrons flow through the wire to the cathode and the protons flow through the electrolyte present. The air saturated cathode accepts the
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Unformatted text preview: protons and electrons to form water as a byproduct. The overall reaction is essentially 2H 2 + O 2 2H 2 O + energy, and since the hydrogen and oxygen gas are kept separate, the energy is not heat, but electrical energy instead (demonstrated by the cell voltage). As hydrogen gas is depleted, the concentration of oxygen is reduced and as a result, the cell voltage decreases. But since oxygen has essentially an infinite supply of air, hydrogen gas is the limiting reagent and the reaction will stop when the supply of hydrogen gas is gone. 5. Due to the reaction 2H 2 O 2H 2 + O 2 , two molecules of Hydrogen gas are created for every one mole of oxygen gas is created, resulting in a greater volume of Hydrogen gas than oxygen gas....
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This note was uploaded on 03/13/2009 for the course CHEM 1A taught by Professor Nitsche during the Spring '08 term at University of California, Berkeley.

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lab #2 - protons and electrons to form water as a...

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