Question Video: Identifying Which Electrode Is Electroplated from a Given Diagram Chemistry • 10th Grade

Which of the following metal electrodes is coated in metal using the electroplating experiment set up in the diagram? [A] Electrode B [B] Electrode C [C] Electrode D [D] Electrode A


Video Transcript

Which of the following metal electrodes is coated in metal using the electroplating experiment set up in the diagram? (A) Electrode B, (B) electrode C, (C) electrode D, or (D) electrode A.

To answer this question, we need to understand how electrons flow in an electroplating electrolysis reaction. In an electrolysis reaction, a power supply is used to generate an electric current that passes through a solution containing ions ,which cause the ions to migrate to charged electrodes. These migrating ions can be metal ions that are used to deposit a more desired type of metal onto the surface of another metal. This process is known as electroplating.

For example, iron, a strong metal that is excellent for utensils like spoons but highly susceptible to rust, can be coated with a metal like tin to avoid corrosion. A reaction like this would be carried out in what is known as an electrolytic cell. These cells are set up very specifically depending on the reaction that is needed.

An electrolytic cell contains an electrolyte. The electrolyte solution allows the circuit to connect between the two electrodes, supplying the metal ions that take place in the reaction. The liquid state of the electrolyte solution allows for the free movement of ions within the cell.

The movement of the metal ions is influenced by the charge of the electrodes. Positive ions, cations, will flow towards the negatively charged cathode. Likewise, the negatively charged ions, anions, will flow to the positively charged anode.

Since we know where the ions will flow, we can anticipate which electrode will be coated in the diagram in our question. Our diagram shows two electrolytic cells that are connected to one power supply with two different electrolyte solutions. The electrolyte solution on the left is sodium chloride, NaCl. The electrolyte solution on the right is silver chloride, AgCl.

Both solutions will yield a negatively charged chloride anion, Cl–, that will migrate to the positively charged anodes. However, since chloride is not a metal, the positively charged anodes will not be coated in metal. We can therefore eliminate answer choices (B) and (D) because they state that the positively charged electrodes will be coated in metal.

So what about the cations? The sodium chloride electrolyte contains a sodium cation, Na+, that will migrate to the negatively charged cathode. Since sodium is highly reactive, it will not deposit onto the surface of an electrode like less reactive metals, such as copper. Instead, hydrogen ions from the water molecules within the aqueous solution will react at the electrode to form hydrogen gas.

The silver chloride electrolyte solution on the right will yield a silver cation, Ag+, that will migrate towards the negatively charged cathode. The silver metal cation will then coat the cathode with pure silver metal, also known as electroplating. So since electrode D, the cathode on the right side, is the only electrode in our apparatus that is coated in metal, we can say that the correct answer is answer choice (C), electrode D.

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