Question

Consider two electrochemical reaqctions. Reaction A results in the transfer of 2 mol of electrons per mole of reactant and generates a current of 5 A on an electrode 2 cm2 in area. Reaction B results in the transfer of 3 mol of electrons per mole of reactant and generates a current of 15 A on an electrode 5 cm2 in area. What are the net reaction rates for reactions A and B (in moles of reactant per square centimeter per second)? Which reaction has the higher net reaction rate?

Answer 1

Answer:

Reaction A has a higher net reaction rate

Explanation:

Rate of electrochemical reaction rate per unit area = $\frac{i}{nFA}$

F = 96500 C$mol^{-1}$ ( Faraday constant)

n = number of moles of electrons per mole of reactant

A = Area of electrode

i = current generated

convert the current from Amperes to C$s^{1}$

To calculate net reaction of reaction A

i = 5 c$s^{1}$

n = 2

A = 2

back to the equation

=  5 / (2 * 96500 * 2) = (1.3 * 10 ^ -5)  mols^-1 cm^-2

To calculate net reaction of reaction B

i = 15 c$s^{1}$

n = 3

A = 5

back to the equation

= 15 / ( 3 * 96500 * 5) =  (1.036 * 10 ^ -5)  mols^-1 cm^-2

Answer 2

Answer:

Reaction A has higher net reaction rate

Explanation:

Data:

The reaction rates:

Reaction A:

Number of electrons per area = 2 mol/ 2 cm²

                                                  = 1 mol/ cm²

Reaction B:

Number of electrons per area = 3 mol/ 5 cm²

                                                  = 0.6 mol/cm²

Based on the calculations above, the reaction B has a higher reaction rate.