The saturated calomel electrode, abbreviated SCE, is often...

The saturated calomel electrode, abbreviated SCE, is often used as a reference electrode in making electrochemical measurements. The SCE is composed of mercury in contact with a saturated solution of calomel $\left(\mathrm{Hg}_2 \mathrm{Cl}_2\right)$. The electrolyte solution is saturated KCl . $\varepsilon_{\text {SCE }}$ is +0.242 V$ relative to the standard hydrogen electrode. Calculate the potential for each of the following galvanic cells containing a saturated calomel electrode and the given half-cell components as standard conditions. In each case, indicate whether the SCE is the cathode or the anode. Standard reduction potentials are found in Table 11.1. a. $\mathrm{Cu}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Cu}$ b. $\mathrm{Fe}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Fe}^{2+}$ c. $\mathrm{AgCl}+\mathrm{e}^{-} \rightarrow \mathrm{Ag}+\mathrm{Cl}^{-}$ d. $\mathrm{Al}^{3+}+3 \mathrm{e}^{-} \rightarrow \mathrm{Al}$ e. $\mathrm{Ni}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Ni}$

The saturated calomel electrode, abbreviated SCE, is often used as a reference electrode in making electrochemical measurements. The SCE is composed of mercury in contact with a saturated solution of calomel $\left(\mathrm{Hg}_2 \mathrm{Cl}_2\right)$. The electrolyte solution is saturated KCl . $\varepsilon_{\text {SCE }}$ is +0.242 V$ relative to the standard hydrogen electrode. Calculate the potential for each of the following galvanic cells containing a saturated calomel electrode and the given half-cell components as standard conditions. In each case, indicate whether the SCE is the cathode or the anode. Standard reduction potentials are found in Table 11.1.
a. $\mathrm{Cu}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Cu}$
b. $\mathrm{Fe}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Fe}^{2+}$
c. $\mathrm{AgCl}+\mathrm{e}^{-} \rightarrow \mathrm{Ag}+\mathrm{Cl}^{-}$
d. $\mathrm{Al}^{3+}+3 \mathrm{e}^{-} \rightarrow \mathrm{Al}$
e. $\mathrm{Ni}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Ni}$

Key Concepts

Saturated Calomel Electrode (SCE)

The saturated calomel electrode is a commonly used reference electrode in electrochemical measurements. It consists of elemental mercury in contact with mercurous chloride (calomel) and a saturated solution of potassium chloride. The SCE has a well-defined, stable potential relative to the standard hydrogen electrode, enabling it to serve as a baseline for measuring electrode potentials of other half-cells.

Standard Reduction Potential

The standard reduction potential is the voltage associated with a reduction half-reaction under standard conditions (1 M solution, 1 atm pressure, and 25°C temperature). It is used as a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. These values are essential for predicting the direction of redox reactions and calculating overall cell potentials.

Galvanic Cell

A galvanic cell, also known as a voltaic cell, is an electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions. It consists of two half-cells, each containing an electrode and its corresponding electrolyte, where the difference in electrode potentials drives the electron flow through an external circuit.

Electrode Potential Calculation

The electrode potential calculation in a galvanic cell involves finding the difference between the potentials of the cathode and the anode. Under standard conditions, this is computed using the formula E_cell = E_cathode - E_anode. This calculation is fundamental to determine the net electromotive force (EMF) of the electrochemical cell.

Anode and Cathode Identification

In any galvanic cell, the anode is where oxidation occurs and the cathode is where reduction takes place. Determining which half-cell serves as the anode or cathode depends on the standard reduction potentials of the electrodes. The electrode with the higher reduction potential tends to act as the cathode, and identifying this is crucial for understanding the direction of electron flow in the cell.

Transcript

00:01 In this problem, we're considering the saturated calomel electrode, abbreviated xce.

00:08 It's often used as a reference electrode in making electrochemical measurements.

00:14 It's composed of mercury in contact with a saturated solution of calomel, which is hg2cl2.

00:43 The electrolyte solution is kcl and e for the fce is plus 20 .242 volts relative to the standard h.

01:28 Okay, in each case, in each case that follows, indicate whether the fce is the cathode or the anode.

01:54 Okay, now i know what we're doing.

01:59 Okay, and we are doing the following.

02:05 My first one, a.

02:10 We have cu plus 2e minus yields this.

02:22 Okay, so let's figure out what we're doing.

02:25 Here.

02:29 So let's go ahead and write the hg2cl2 plus 2e and this will be 2hgl plus 2cl minus and here my e cell or sce is 0 .242 volts.

03:03 Okay this is what we're considering for each one of now for my copper, this is 0 .34 volts as written.

03:16 So this is going to be my cathode.

03:28 This is going to be my anode.

03:56 And if i include that it's anode, let's do this.

04:05 And this is positive 0 .34.

04:09 This will be negative 0 .242.

04:13 I'm going to have to reverse this reaction...

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