Batteries are galvanic cells. What happens to as a battery discharges? Does a battery represent a system at equilibrium? Explain. What is when a battery reaches equilibrium? How are batteries and fuel cells alike? How are they different? The U.S. space program utilizes hydrogen–oxygen fuel cells to produce power for its spacecraft. What is a hydrogen–Oxygen fuel cell?

Interpretation:

Batteries being galvanic cells and the use of hydrogen-oxygen by the U.S. space program to produce power for its spacecraft are given. The concept behind the working of fuel cells and battery is to be stated.

Concept introduction:

Batteries are a combination of galvanic cells. Just like galvanic cell, the value of cell potential decreases as the battery discharges and attains the zero value at equilibrium.

Fuel cells are also used for the generation of electricity. The hydrogen-oxygen fuel cells are used for the power generation in the spacecraft and they are eco-friendly.

To determine: The effect of discharge of battery over Ecell ; effect of equilibrium over the system and; similarities and differences between battery and fuel cells; the concept of hydrogen-oxygen fuel cell

There occurs decrease in Ecell as the battery discharges and it almost tends towards zero.

During discharging, the electrons transfer from anode to cathode and this neutralizes the negative charge over the cathode. Due to this, the potential difference between anode and cathode decreases and finally approaches zero.

The battery can represent a system at equilibrium, but Ecell=0 at equilibrium.

At equilibrium, the value of cell potential comes out to be zero and hence, no work can be obtained from the battery at equilibrium.

At equilibrium Ecell attains the value of zero.

At equilibrium Ecell becomes zero and therefore the Gibbs free energy change is also zero and therefore the useful work cannot be obtained for a system present at the equilibrium state.

The battery and fuel cells are alike in the manner that both are the galvanic cells.

Both the battery and the fuel cell are the galvanic cell that are used for the generation of useful work.

The battery and fuel cells are different in the sense that battery does not require supply of reactants to carry out a reaction, while the fuel cells require continuous feeding of reactants to carry out a reaction.

The reactants required for the generation of electricity are already present inside the battery, but for a fuel cell to work out, the reactant have to be supplied continuously. Fuel cells will work till the time the reactants are supplied to them.

In the hydrogen-oxygen fuel cell, a porous anode and a cathode have an electrolyte sandwiched between them. Hydrogen is supplied to the anode and a catalyst separates the electrons from protons, while the oxygen at the cathode combines with the electrons and leads to the formation of hydroxide ions