Final answer:
To calculate the voltage produced by a hydrogen fuel cell under acidic conditions, one must use the Nernst equation, considering the concentration of hydrogen ions and the standard reduction potentials, rather than a straightforward formula involving pH and the Faraday constant.
Step-by-step explanation:
The voltage produced by a hydrogen fuel cell under acidic conditions does not follow a direct formula involving the pH and Faraday constant, such as 'pH x Faraday constant', 'Faraday constant / pH', 'pH + Faraday constant', or 'Faraday constant - pH'. Instead, the cell voltage is typically determined using the Nernst equation, where you would take into account the reduction potential of the hydrogen electrode and the pH of the solution. The cell voltage can be calculated by substituting the known values into the Nernst equation and solving for the cell potential. For instance, if you have a hydrogen fuel cell operating under acidic conditions, you would need to know the concentration of hydrogen ions to calculate the pH and then use this information along with standard reduction potentials to find the cell voltage.
Nevertheless, given the context provided, none of the options a) through d) directly provide a method for calculating the cell voltage. The cell potential of hydrogen fuel cells, like the one described with a pH of 8.5, can be calculated but typically requires a more complex understanding and application of electrochemistry principles beyond a simple algebraic combination of the pH and the Faraday constant. It's important to note that the standard electrode potential for the hydrogen cell is -1.229 V, and practical electrolysis of water would require additional voltage due to over voltages.