a. Write the half-reactions for a H2-O2H₂-O₂ fuel cell. Find the theoretical cell voltage at 25°C 25°C if PH2=1.0 bar, PH₂=1.0 bar, PO2=0.2 bar PO₂=0.2 bar and [H+]=0.5 M[H⁺] = 0.5 M at both electrodes. (Real fuel cells operate at temperatures of 60° -1 000°C 60° -1 000°C and produce ~0.7 V.~0.7 V.)
b. If the cell is 70% 70% efficient at converting chemical energy into electrical energy, and a stack of cells produces 20 kW 20kW at 220 V, 220 V how many grams of _H2H₂ are consumed in an hour?
c. In the United States, engines are frequently rated in “horsepower.” Use Table 1-4 to convert 20 kW 20 kW to horsepower.

Table 1-4

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TABLE 1-4 Conversion factors Quantity Volume Length Mass Force Pressure Energy Unit liter Power milliliter angstrom inch pound metric ton dyne bar atmosphere atmosphere atmosphere torr (-1 mm H torr (= 1 mm Hg) pound/in.2 pound/in.² erg electron volt calorie, thermochemical Calorie (with a capital C) British thermal unit horsepower Temperature centigrade Celsius) Fahrenheit Celsius) Symbol L mL A in. lb dyn bar atm atm atm Torr psi erg eV cal Cal Btu °C C °F F SI equivalent *10-3 m3*10-3 m³ *10-6 m3*106 m³ *10-10 m*10-10 m *0.025 4 m *0.025 4 m *0.453 592 37 kg *0.453 592 37 kg *1 000 kg *1 000 kg *10-5 N*10* N *105 Pa* 105 Pa *101 325 Pa *101 325 Pa *1.013 25 bar *1.013 25 bar 760 mm Hg-760 torr 760 mm Hg = 760 torr 133.322 Pa133.322 Pa 6 894.76 Pa6 894.76 Pa *10-7J*10-7 J 1.602 176 634×10-19 11.602 176 634 x 10-¹9 J *4.184 J*4.184.J *1 000 cal-4.184 kJ *1 000 cal = 4.184 kJ 1055.06 J1 055.06 J 745.700 w745.700 W *K-273.15 *K-273.15 2*1.8(K-273.15) + 32 *1.8(K-273.15)+32