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# A10 - PHYS 258 Thermal Physics Student ID Assignment 10...

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PHYS 258 - Thermal Physics: Assignment 10 Due Monday April 4 Student ID: Full Name: Score:________/16_____ 1. [6] Methane (Natural Gas) Fuel Cell. Consider a fuel cell that uses methane as fuel. The chemical reaction is energy CO O H O CH + + 2 2 2 4 2 2 + (a) Measurements reveal that Δ H for this reaction is - 890 kJ for each mole of methane processed, assuming standard temperature and pressure ( T =298 K, P =10 5 Pa). Ignoring the volume of the liquid H 2 0, use the ideal gas law to estimate the change in volume during this reaction, and thus determine the amount of energy we get for “free” from the collapsing environment. (b) Using the appropriate table at the back of the textbook (or elsewhere), look up the entropies of the various chemicals involved in the above reaction (at standard temperature and pressure) and thus compute Δ S , the change in entropy for each mole of methane processed. Thus evaluate Δ G T,P , the change in the Gibbs free energy (at standard temperature and pressure) for each mole of methane processed.

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(c) Assuming ideal performance, how much electrical work can you get out of the cell for each mole of methane fuel? = (d) How much waste heat must be dumped into the environment for each mole of methane fuel? (e) What is the theoretical maximum “efficiency" of this fuel cell? (f) In more detail, the above chemical reaction proceeds in two steps that are happening simultaneously at the positive and negative electrodes of the fuel cell: at - electrode:
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A10 - PHYS 258 Thermal Physics Student ID Assignment 10...

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