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Chapter 17: Problem 108

Copper can be plated onto a spoon by placing the spoon in an acidic solution of \(\mathrm{CuSO}_{4}(a q)\) and connecting it to a copper strip via a power source as illustrated below: a. Label the anode and cathode, and describe the direction of the electron flow. b. Write out the chemical equations for the reactions that occur at each electrode.

Short Answer

Expert verified
In this electroplating process, the copper strip serves as the anode and the spoon serves as the cathode. Electrons flow from the copper strip (anode) to the spoon (cathode) through the power source. At the anode, oxidation occurs, and the half-reaction is: \(\mathrm{Cu(s) \rightarrow Cu^{2+}(aq) + 2e^{-}}\). At the cathode, reduction occurs, and the half-reaction is: \(\mathrm{Cu^{2+}(aq) + 2e^{-} \rightarrow Cu(s)}\).

Step by step solution

01

Identify the Anode and Cathode

Firstly, we need to identify which of the two electrodes is the anode and which is the cathode. The anode is the electrode where oxidation occurs, and the cathode is the electrode where reduction occurs. In the given process, the copper strip loses its copper ions by providing them to the acidic solution of \(\mathrm{CuSO}_{4}\). Therefore, the copper strip is the anode. The spoon, on the other hand, gains copper ions from the solution and is plated with copper. Hence, the spoon serves as the cathode.
02

Determine Electron Flow Direction

Now, we should describe the direction of electron flow in the circuit. Electrons always flow from anode to cathode in an electrochemical cell. So, the electrons flow from the copper strip (anode) to the spoon (cathode) through the power source (battery).
03

Write Chemical Equations for Anode Reaction

At the anode (copper strip), we have an oxidation process, where the solid copper metal loses electrons to become copper ions which go into the solution. The half-reaction for this process can be written as: \[ \mathrm{Cu(s) \rightarrow Cu^{2+}(aq) + 2e^{-}}\]
04

Write Chemical Equations for Cathode Reaction

At the cathode (spoon), we have a reduction process, where copper ions from the solution gain electrons and become solid copper metal, depositing on the spoon. The half-reaction for this process can be written as: \[ \mathrm{Cu^{2+}(aq) + 2e^{-} \rightarrow Cu(s)}\] These are the chemical reactions occurring at each electrode during the electroplating process.

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Most popular questions from this chapter

When copper reacts with nitric acid, a mixture of \(\mathrm{NO}(g)\) and \(\mathrm{NO}_{2}(g)\) is evolved. The volume ratio of the two product gases depends on the concentration of the nitric acid according to the equilibrium $$2 \mathrm{H}^{+}(a q)+2 \mathrm{NO}_{3}^{-}(a q)+\mathrm{NO}(g) \rightleftharpoons 3 \mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)$$ Consider the following standard reduction potentials at \(25^{\circ} \mathrm{C}:\) $$\begin{aligned} &3 \mathrm{e}^{-}+4 \mathrm{H}^{+}(a q)+\mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{NO}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)\ & \mathscr{E}^{\circ}=0.957 \mathrm{V} \end{aligned}$$ $$\begin{aligned} &\mathrm{e}^{-}+2 \mathrm{H}^{+}(a q)+\mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{NO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) &\mathscr{E}^{\circ}=0.775 \mathrm{V} \end{aligned}$$ a. Calculate the equilibrium constant for the above reaction. b. What concentration of nitric acid will produce a NO and \(\mathrm{NO}_{2}\) mixture with only \(0.20 \% \mathrm{NO}_{2}\) (by moles) at \(25^{\circ} \mathrm{C}\) and 1.00 atm? Assume that no other gases are present and that the change in acid concentration can be neglected.

The measurement of \(\mathrm{pH}\) using a glass electrode obeys the Nernst equation. The typical response of a pH meter at \(25.00^{\circ} \mathrm{C}\) is given by the equation $$ \mathscr{E}_{\text {meas }}=\mathscr{E}_{\text {ref }}+0.05916 \mathrm{pH} $$ where \(\mathscr{E}_{\text {ref }}\) contains the potential of the reference electrode and all other potentials that arise in the cell that are not related to the hydrogen ion concentration. Assume that \(\mathscr{E}_{\mathrm{ref}}=0.250 \mathrm{V}\) and that \(\mathscr{E}_{\text {meas }}=0.480 \mathrm{V}\) a. What is the uncertainty in the values of \(\mathrm{pH}\) and \(\left[\mathrm{H}^{+}\right]\) if the uncertainty in the measured potential is \(\pm 1 \mathrm{mV}\) \((\pm 0.001 \mathrm{V}) ?\) b. To what precision must the potential be measured for the uncertainty in \(\mathrm{pH}\) to be \(\pm 0.02 \mathrm{pH}\) unit?

In the electrolysis of a sodium chloride solution, what volume of \(\mathrm{H}_{2}(g)\) is produced in the same time it takes to produce \(257 \mathrm{L}\) \(\mathrm{Cl}_{2}(g),\) with both volumes measured at \(50 .^{\circ} \mathrm{C}\) and 2.50 atm?

A solution containing \(\mathrm{Pt}^{4+}\) is electrolyzed with a current of 4.00 A. How long will it take to plate out \(99 \%\) of the platinum in 0.50 L of a \(0.010-M\) solution of \(\mathrm{Pt}^{4+} ?\)

An electrochemical cell consists of a nickel metal electrode immersed in a solution with \(\left[\mathrm{Ni}^{2+}\right]=1.0 \mathrm{M}\) separated by a porous disk from an aluminum metal electrode. a. What is the potential of this cell at \(25^{\circ} \mathrm{C}\) if the aluminum electrode is placed in a solution in which \(\left[\mathrm{Al}^{3+}\right]=7.2 \times\) \(10^{-3} M ?\) b. When the aluminum electrode is placed in a certain solution in which \(\left[\mathrm{Al}^{3+}\right]\) is unknown, the measured cell potential at \(25^{\circ} \mathrm{C}\) is \(1.62 \mathrm{V}\). Calculate \(\left[\mathrm{Al}^{3+}\right]\) in the unknown solution. (Assume Al is oxidized.)
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