What reaction will take place at the cathode and the anode when each of the following is electro

step 1 Okay, this question is similar to 111 .11. We need to consider whether or not the cation is goin

What reaction will take place at the cathode and the anode...

Key Concepts

Electrolysis

Electrolysis is the process of driving a non-spontaneous chemical reaction by applying an external electrical energy. It involves the movement of ions in an electrolyte toward electrodes where reduction and oxidation occur, allowing the separation or transformation of chemical species in solution.

Reduction Reaction at the Cathode

At the cathode, reduction takes place as electrons are supplied by the external circuit to species in the solution. Typically, species with higher (more positive) reduction potentials are reduced; however, in aqueous solutions, water can often be reduced instead of certain cations when their reduction is less favorable. This concept is key to predicting which species will accept electrons and be transformed at the cathode during electrolysis.

Oxidation Reaction at the Anode

Oxidation occurs at the anode where electrons are withdrawn from species in the solution, leading to potential formation of gaseous products or different chemical entities. The species with lower oxidation potentials, or those that can be more easily oxidized, will typically undergo oxidation. In aqueous systems, water might also be oxidized if the anions present are not easily oxidized, illustrating the importance of comparing oxidation potentials in reaction prediction.

Standard Electrode Potentials

Standard electrode potentials provide a measure of the tendency of a chemical species to be reduced or oxidized under standard conditions. These values are essential for determining which redox reactions will occur preferentially during electrolysis. By comparing these potentials, one can predict whether a cation or water will be reduced at the cathode, or whether an anion or water will be oxidized at the anode.

Aqueous Media Electrolysis

When electrolysis is performed in an aqueous solution, water becomes an important participant in the redox processes. Depending on the relative potentials of the solute ions compared to water, water may be reduced or oxidized instead of the dissolved ions. This interplay is critical in analyzing the overall reaction mechanisms and products in the electrolysis of aqueous solutions.

Electrode Selectivity and Overpotential

Electrode selectivity and overpotential are factors that influence which reactions actually occur at the electrodes. Overpotential refers to the extra potential needed beyond the theoretical value to drive a reaction at a significant rate. This means that even if thermodynamics suggests a certain reaction is feasible, kinetic factors—including the electrode material and reaction mechanism—can favor alternative reactions. Understanding these concepts is essential for accurately predicting electrolysis outcomes.

Transcript

00:01 Okay, this question is similar to 111 .11.

00:03 We need to consider whether or not the cation is going to be reduced or water is going to be reduced.

00:11 Or whether the anion is going to be, or we need to consider whether the anion is going to be oxidized or oxygen is going to be oxidized.

00:20 So for the first salt, we have potassium to cation with a reduction potential of negative 2 .92 volts.

00:27 The water reduction potential is negative .83 volts because water has a greater reduction potential than potassium than water will be reduced at the cathode.

00:39 The oxidation potential for fluoride going to fluorine is the opposite of the reduction potential of fluorine going to fluoride.

00:51 So it's negative 2 .87 instead of positive 2 .87 as it is shown in the table.

00:56 And then water has an oxidation potential of negative 1 .23 volts.

01:02 Because negative 1 .23 volts is greater than the negative 2 .87 volts, than water also is now going to be oxidized at the anode.

01:14 Then going on to b, the potential reduction, half reaction, is copper 2 plus going to copper solid from the salt.

01:24 But there's also a potential reduction reaction for water going to hydrogen gas and hydroxide.

01:32 We look up the reduction potential for copper at positive 0 .34 volts, and then we look at the reduction potential for water at negative 0 .83 volts, because copper has a higher reduction potential, then it will be the one that is reduced.

01:46 It wants to be reduced more than water...

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