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    Stoichiometry Question

    NASAs long term plans for sending astronauts to Mars involves an ISRU strategy. ISRU is in-situ resource utilization and means that to the extent possible, chemical resources already on Mars will be utilized. The Martian atmosphere contains about 95.3% carbon dioxide. According to one NASA plan, hydrogen will be sent to Mars from Earth before astronaut crews arrive. Fuel for the Mars Ascent Vehicle (MAV) will consist of methane-oxygen combustion: CH4 + 2O2  CO2 + 2H2O. The fuel and oxygen will be made by the following reactions:

    CO2 + 4H2CH4 + 2H2O (the Sabatier reaction)
    And 2H2O2H2 + O2 (the electrolysis of water)
    Energy to run these latter reactions will come perhaps from Plutonium power sources or solar cells. Making use of the above reactions, calculate the minimum mass of hydrogen that will have to be sent from Earth to Mars in order to produce 500 kg of methane and the necessary oxygen to combust it.

    © BrainMass Inc. brainmass.com May 24, 2023, 1:10 pm ad1c9bdddf

    Solution Preview

    We need to produce 500 Kg of CH4.

    Therefore number of moles of CH4 = weight/mol. mass = 500*10^3/16
    = 31250 moles

    Now, we have the reaction,
    CO2 + 4H2 - gt; CH4 + 2H20

    It implies,
    4 moles of H2 give 1 mole CH4
    That is,
    to obtain 31250 CH4, we need 4*31250 moles of H2 = 125000 moles of H2

    Therefore, mass of H2 = moles * mol mass
    = 12500 * 2
    = 250000 g
    = 250 Kg

    2CH4 + 4O2 - 2CO2 + 4H20
    That is 2 mole ...

    Solution Summary

    The expert analyzes fuel and oxygen in Sabatier reaction and electrolysis of water. The minimum mass of hydrogen that will have to be sent form Earth to Mars is determined. The solution includes formulas, calculations, and answers.