A hydrogen-oxygen fuel cell is operated at 25^∘ C and a total pressure of 5 bar. What is the ele

A hydrogen-oxygen fuel cell is operated at 25^∘ C and a...

Labs

Want to see this concept in action?

NEW

Explore this concept interactively to see how it behaves as you change inputs.

View Labs

Key Concepts

Electromotive Force (EMF)

This is the voltage difference generated by an electrochemical cell under non-equilibrium conditions. It represents the driving force for electron flow in the cell and is determined by both the intrinsic properties of the cell’s materials and the operating conditions, such as temperature and pressure.

Nernst Equation

This equation relates the cell potential to the standard electrode potential and the activities (or pressures/concentrations) of the reactants and products. It provides a way to calculate the electromotive force under non-standard conditions by taking into account the effect of concentration or pressure differences on the cell voltage.

Reaction Quotient

The reaction quotient is the ratio, at any point in the reaction, of the activities (or partial pressures or concentrations for gases or solutions) of the products to those of the reactants, each raised to the power of its stoichiometric coefficient. It is used in the Nernst equation to account for deviations from standard conditions.

Ideal Gas Behavior

Assuming that the gases behave ideally allows one to equate their partial pressures directly with their activities. This simplifies the calculation of the reaction quotient and, consequently, the adjustment of the standard electrode potential using the Nernst equation.

Transcript

00:01 So here we have a specific reaction where we have hydrogen reacting of oxygen gas to form 2h2o.

00:08 And we see that we have hydrogen going from 0 to plus 1 oxidation state, oxygen going from 0 to minus 2 oxidation state.

00:18 So essentially the net number of electrons transferred in order for this process to occur is we essentially have to have four moles of electrons transferred in order for this process, since we see that o2 goes from its zero oxidation state, so 2o and 0, then goes to 2 in the minus 2 state.

00:39 So this would require four electrons in order for this process to occur.

00:44 And we're given that the current is equipped for this process is 1 .5 ampires.

00:48 And we're given that we have excess oxygen.

00:52 And so we don't have to worry about that.

00:54 And we have a certain amount of hydrogen.

00:56 So you have 1 liters and 200 bars.

01:00 And we have 25 degrees celsius, which is 298 kelvin.

01:05 So you have to use pv equals nrt.

01:07 So we're going to be careful with our gas constant.

01:10 We have to use the bar form of the gas constant, which is the following.

01:15 So per mole kelvin's.

01:17 And now we have essentially sufficient information to solve for the number of moles of hydrogen present...