b. 050 points 5 attempts left Check my work Be sure to answer all parts. The hyd

Question

b. 050 points 5 attempts left Check my work Be sure to answer all parts. The hydrogen-oxygen fuel cell is described in the text. For the questions below, assume the followings Assume that the air is 20 % O2 by volume and that all the O2 is consumed in the cell. The other components of air do not affect the fuek-cell reactions. Assume ideal gas behavior. (a) What volume of H2(g), stored at 25.0°C at a pressure of 157 atm, would be needed to run an electric motor drawing a current of 8.50 A for 3.00 hr ? (b) What volume (in liters) of air at 25.0°C and 1.07 atm will have to pass into the cell per minute to run the motor ? L/min

Explanation / Answer

a)

mol of e- --> get Charge

Charge = I*t = (8.5)(3*3600) = 91800 C

1 mol ofe- = 96500 C

mol of e- = 0.9512 mol of e-

2 mol of e- = 1 mol of H2

0.9512 mol --> 0.9512/2 =0.4756mol of H2

PV = nRT

V = nRT/P

V = 0.4756*0.082*298/157

V = 0.0740 L

b)

find V for:

air --> 1.07 atm

H2 + 1/2O2 = H2O

mol of O2 required --> 1/2*0.4756 = 0.2378 mol of O2

PV = nRT

V = nRT/P = (0.2378)(0.082)(298)/1.07

V = 5.43072 L of O2

20% is O2 --> 5.43072/0.2 = 27.1536 L of air

this is in 3 hours --> 3*60 180 min

V = 27.1536 /180

V= 0.15085 L of air/ min

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