In a hydrogen/oxygen fuel cell 67.2 litres of hydrogen is consumed in 5 minutes. What electric current will be produced at #sf(0^@C)# and 1 atmosphere pressure ?
We are given:
Use the factor that converts Liters to Moles:
Please observe how the units cancel:
We know that 1 mole of H
Use Avagadro's Constant :
Next we use the definition of a Coulomb :
Because we know that an Ampere is 1 Coulomb per second we must convert minutes to seconds:
Do the multiplication and division and the answer will be in Amperes:
This seems reasonable, because the consumption rate of Hydrogen is quite high and the potential of a single cell is between 0.6 and 0.7 volts, thereby, making the output power about 1.3 kW. To practically do this, one would stack the cells in a series-parallel configuration.
Hydrogen is oxidised at the anode:
This tells us that 1 mole of
The charge on 1 mole of electrons is given by the Faraday Constant and is equal to
So the total charge Q produced is given by:
This is produced in 5 minutes which = 5 x 60 = 300 s.
Electric current I is the rate of flow of charge as given by: