# Hi, I have a chemical engineering assignment that will be available at 2:00 and needs to be submitted by 4:00. Do you have a live agent/tutor who can be live to help during that time? Assignment will

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Hi, I have a chemical engineering assignment that will be available at 2:00 and needs to be submitted by 4:00. Do you have a live agent/tutor who can be live to help during that time? Assignment will be 1 or 2 questions similar to the ones attached, specifically problem 2

Hi, I have a chemical engineering assignment that will be available at 2:00 and needs to be submitted by 4:00. Do you have a live agent/tutor who can be live to help during that time? Assignment will

MAE 1 6:650: 605 Alternative Energy Systems I I Homework 7 Instructions 1. Due April 27, 20 21 by 11:30 pm. 2. Complete ALL of the problems listed below. 3. Make a PDF of the homework assignment and upload 1 file electronically through CANVAS . 4. The course name, number and student’s full name must be listed at the top of each page. Description Number of Points H OMEWORK FORMAT AND GUIDELINES Document legibility 2 Name of the student, class name and number on the top of every page of the assignment. 3 Problem 1 10 Problem 2 25 Problem 3 15 Problem 4 10 Problem 5 15 Problem 6 20 T OTAL POINTS 100 MAE 1 6:650: 605 Alternative Energy Systems I I Problem 1 (10 points) A direct methanol fuel cell uses methanol as a fuel instead of hydrogen. Calculate the Δℎ̂ and Δ̂ methanol combustion reaction where a) liquid water is produced and b) vapor water is produced. Determine the change in Gibbs Free Energy for the reaction at standard conditions of T = 298.15K and P = 1 atm . Assume the methanol in both cases is a gas. Also, assume that you ar e examining the case where liquid water is produced. 1. If liquid water is produced. 2. If vapor water is produced. MAE 1 6:650: 605 Alternative Energy Systems I I Problem 2 (25 points) For a fuel cell that has an overall fuel cell reaction, where q = constant electron charge = 1.60 x 10 -19 Coulomb, No = Avogadro’s number = 6.02 x 10 23 atoms/mol: Determine the following (Assume the water produced is liquid) : a) The approximate temperature at which the above reaction is no longer spontaneous assuming the enthalpy and the entropy of reaction are independent of the temperature, i.e. the heat capacity effects are negligible. (will acc ept answers for liquid or vapor) b) The approximate temperature at which the above reaction is no longer spontaneous assuming that the enthalpy and the entropy of the reaction are NOT independent of t he temperature, i.e. the heat capacity effects cannot be neglected, and must be taken into account. Assume the heat capacity values are constant and taken at standard temperature and pressure. MAE 1 6:650: 605 Alternative Energy Systems I I MAE 1 6:650: 605 Alternative Energy Systems I I The plots from this demonstrate that thi s reaction will always be ther modynamically predicted to be spontaneous. MAE 1 6:650: 605 Alternative Energy Systems I I c) Determine the reversible work when the operation temperature o f the cel l is equal to 800 °K for MAE 1 6:650: 605 Alternative Energy Systems I I the using assumptions of constant enthalpy and entropy li ke in a) and non -consta nt enthalpy and entropy, i.e. variable as a function of temperature li ke in b) . d) Determine t he output voltage for the cell for the conditions specified in c). e) Determine t he reversible thermal efficiency for the fuel cell for conditions specified in a) and b) . Is there a difference in the reversible thermodynamic efficiency? MAE 1 6:650: 605 Alternative Energy Systems I I Problem 3 (15 points) Consider a hydrogen -concentration fuel cell is examined a concentration cell, that consists of pressurized hydrogen fuel compartment and an evacuated ultra -low – pressure vacuum compartment separated by a composite platinum -electrolyte -platinum membrane structure . This cell contains no oxygen to react with the hydrogen, yet it will produce energy. If the hydrogen compartment is pressurized to 150 atm H 2 and the vacuum compartment is evacuated to 10 -7 atm, what voltage will this unit produced as determined by the Nernst equation? Problem 4 (10 points) A typical H2 -O2 PEMFC might operate at a voltage of 0.75 V and stoichiometric factor, = 1.10. At Standard State -Condition s for Ambient of Temperature Pressure (T=298.15 K and P=1 atm) , what is the efficiency of such a fuel cell? Use HHV (high heating v alue) and assume oxygen at the cathode. Problem 5 (1 5 points) Consider two electrochemical reactions: A and B. Reaction A results in the transfer of 2 mol of electrons per mole of reactant and generates a current of 5 Amps on an electrode 2 cm 2 in area. Reaction B results in the transfer of 3 mol of electrons per mole of reactant and generates a current of MAE 1 6:650: 605 Alternative Energy Systems I I 15 Amps on an electrode having 5 cm 2 in area. What are the net reaction rates for reactions A and B (in mol reactant per square centimeter per second)? Which reaction has the higher net reaction rate? Problem 6 (20) Everything else being equal, write a general expression to show how the exchange current density for a reaction changes as a function of temperature. In other words, write an e xpression for j 0(T) at an arbitrary temperature T as a function of j 0(T 0) at a reference temperature T 0. If a reaction has j 0 = 10 -8 A/cm 2 at 300K and j 0 = 10 -4 A/cm 2 at 600K, what is ∆1 ++ for the reaction? Assume that the T 0 is 300K.

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