Assessment of Fuel Cell Modifications for CHEM-237
Final Exam:
Question #2: Hydrogen Storage and Gas Law Stoichiometry:
An aqueous solution of 30% (by mass) NaBH4 (Molecular weight: 44 g/mole) is used to
store hydrogen. Hydrogen gas is produced by adding a catalyst to the solution to promote
the following reaction:
NaBH4 + 2H2O -------! NBO2 + 4 H2
How many grams of the solution are needed in order to produce 1000 L of hydrogen gas
at 25oC and 1 atm pressure.
Individual Grades:
Average: 5.9/8 = 74%
Question # 13: Hydrogen oxygen fuel cell, Standard Cell Potential,
Nernst Equation, ∆Go
13. (12 points) An alkaline hydrogen-oxygen fuel cell consists of the following half-
cells:
Anode: H2(g) + 2 OH-(aq) --------! 2H2O(l) + 2e
Cathode: 1/2O2(g) + H2O(l) + 2e -------! 2OH-
a. What is the overall cell reaction of this fuel cell?
b. What is the cell potential when the cell is operated at standard condition
(25oC, PH2 = 1.0 atm, PO2 = 1.0 atm, [OH-] = 1.0 M)?
c. Use the Nernst equation to calculate the cell potential when it is operated at
25oC, PH2 = 0.5 atm, PO2= 0.21 atm, and [OH-] = 1.0 M?
d. What is the standard free energy change (∆Go) of the overall cell reaction?
Individual Grades:
Average: 7/12 = 58%
