Question

Make a sketch of an electrolysis cell that could be used to electroplate copper onto other metal surfaces. Label the anode and the cathode and show the reactions that occur at each.

Short answer

The anode is made of copper and connected to the positive terminal, the cathode is the metal surface connected to the negative terminal. Oxidation occurs at the anode: \(Cu \rightarrow Cu^{2+} + 2e^-\), and reduction occurs at the cathode: \(Cu^{2+} + 2e^- \rightarrow Cu\).

Step-by-step solution

Sketch the Electrolysis Cell

Draw a container that will serve as the cell for the electrolysis process. Within this container, place two electrodes: one is the anode and the other is the cathode. The anode is typically made of copper while the cathode is the metal surface onto which the copper will be electroplated. Also, draw a wire connecting the anode and cathode, which will conduct electricity through the circuit, and include a battery or power source in the circuit.

Label the Anode and Cathode

Label the copper electrode as the anode and the metal surface electrode as the cathode. Indicate the direction of electron flow in the external circuit, with electrons traveling from the anode to the cathode. Also, indicate the polarity of each electrode relative to the battery: the anode connected to the positive terminal and the cathode connected to the negative terminal.

Indicate the Reactions

At the anode (positive electrode), indicate the oxidation reaction, where copper atoms lose electrons to form copper ions: \(Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-\). At the cathode (negative electrode), illustrate the reduction reaction, where copper ions in the electrolyte gain electrons to form copper metal: \(Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)\).

Key concepts

Electroplating Process

The electroplating process is like painting with electricity. It involves depositing a thin layer of metal, such as copper, onto another metal surface. Imagine it as using electric current to glue one metal onto another. Think of an electrolysis cell as a craft station where this magic happens.

To set up the station for electroplating, you start with a container that holds the electrolyte solution—this can be thought of as a special 'metal glue'. This solution contains ions of the metal you want to plate, like copper ions if you want to create a copper coating. Then you need two special rods called electrodes: one is the anode, made of the metal you're plating with, and the other is the cathode, the metal surface you want to decorate. When you turn on the power, the electric current pulls metal atoms from the anode and deposits them onto the cathode, dressing it up in a new metal coat.

The beauty of the process is that you can control how thick the metal coat is by adjusting how long the power is on. If you want a thicker layer, electroplate for more time; a thinner layer, less time. This process is widely used to enhance an object's resistance to corrosion, improve solderability, reduce friction, improve paint adhesion, and to increase thickness.

Anode and Cathode Labeling

Imagine electrodes in an electroplating setup as being the positive and negative ends of a battery—because that’s essentially what they are in terms of charge. The anode and cathode are key players. The anode is connected to the positive side of the power source, and the cathode is cozy with the negative side.

Label Them Right

Labelling them is like giving each player a jersey. The anode wears the '+' jersey, and it's where the metal (say, copper) gives up its electrons. The cathode wears the '-' jersey, and it's where the metal bathes in the glory of gained electrons to form a firm metal shell over the surface. It's important to label them correctly because they serve opposite purposes. One gives away, and the other accepts. If you switch their jerseys, you'll end up with a confused process that might give you a surface with less metal instead of more. Getting the labels right ensures that the play of electrons goes smoothly and your metal surface gets a shiny new coat.

Oxidation and Reduction Reactions

In the world of chemistry, oxidation and reduction are like two dance partners in the Tango of Reactions. They always go hand in hand. Oxidation is when an element loses electrons—a bit like spending cash. Reduction is the opposite: gaining electrons—like saving up cash.

The Electrons’ Dance

During electroplating, the anode is the dance floor for oxidation. Say it's made of copper. When the power is on, copper atoms strut their stuff by losing two electrons each, transforming into positively charged copper ions. This action is written in science as: \(Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-\).

On the other side, at the cathode, the reduction part of the dance happens. Copper ions from the electrolyte snag two electrons and settle as solid copper on the cathode’s surface. Picture these ions as shoppers finally buying something after saving up enough—a process put into an equation as: \(Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)\). This duo of reactions keeps the electroplating dance flowing, adding a metallic sparkle to the surface of the cathode. Understanding this electron exchange is essential as it's the foundation of how electroplating transforms metal surfaces into something more valuable and durable.