Electrochemical Cell Cell (or line) notation = short hand notation for voltaic cells Example: Zn(s) | Zn”(aq) Cu (aq) Cu (s) The left side represents (oxidation or reduction) The right side represents _loxidation or reduction) The single vertical line represents: The double vertical line represents: Zn2+ (aq) | Brz (1) Br (aq) | Pt (5) Consider the cell notation Zn (s) What is the purpose of the Pt? Write a balanced redox reaction for the above notation. Work through Example 17.3, then write the following reaction using cell notation: 2Ag (aq) + Nils) – Ag(s) + Ni*(aq)
The Correct Answer and Explanation is :
Cell notation is a shorthand method of representing the components of a voltaic cell. This notation helps to identify the materials involved in the reactions occurring in a voltaic cell, as well as the direction of electron flow and where oxidation and reduction occur.
Let’s first break down the example notation:
Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s)
- The left side (Zn(s) | Zn²⁺(aq)) represents the oxidation half-reaction. This is where zinc is losing electrons (oxidation) and going into the solution as Zn²⁺ ions.
- The right side (Cu²⁺(aq) | Cu(s)) represents the reduction half-reaction. In this case, Cu²⁺ ions in solution gain electrons to form solid copper.
- The single vertical line (|) represents the phase boundary between the solid and aqueous states of the substances. So, between Zn(s) and Zn²⁺(aq), and between Cu²⁺(aq) and Cu(s).
- The double vertical line (||) represents the salt bridge or porous barrier that separates the two half-cells while allowing ions to flow between them, completing the electrical circuit.
Purpose of Pt:
In some cases, like in the example with Zn²⁺ (aq) | Br₂ (l) | Br⁻ (aq) | Pt, platinum (Pt) is used as an electrode when there is no solid metal involved in the half-reaction. Platinum provides a surface for electron transfer in reactions involving gases or ions.
Example of a Balanced Redox Reaction for the Given Notation:
Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s)
The oxidation half-reaction (at the anode, where oxidation occurs) is:
[ \text{Zn}(s) \rightarrow \text{Zn}^{2+}(aq) + 2e^- ]
The reduction half-reaction (at the cathode, where reduction occurs) is:
[ \text{Cu}^{2+}(aq) + 2e^- \rightarrow \text{Cu}(s) ]
The overall balanced redox reaction is:
[ \text{Zn}(s) + \text{Cu}^{2+}(aq) \rightarrow \text{Zn}^{2+}(aq) + \text{Cu}(s) ]
Writing the Reaction Using Cell Notation:
The redox reaction is:
[ 2\text{Ag}^+(aq) + \text{Ni}(s) \rightarrow \text{Ag}(s) + \text{Ni}^{2+}(aq) ]
The cell notation for this reaction is:
[ \text{Ni}(s) | \text{Ni}^{2+}(aq) || \text{Ag}^+(aq) | \text{Ag}(s) ]
In this case:
- The left side represents the oxidation half-reaction at the anode (Ni is oxidized to Ni²⁺).
- The right side represents the reduction half-reaction at the cathode (Ag⁺ is reduced to Ag).
- The double vertical line (||) represents the salt bridge or porous barrier.
I’ll now generate an image based on this explanation.
Here is the diagram of the voltaic cell with the zinc and copper half-cells, the salt bridge, and the labels for oxidation and reduction reactions. This visual should help clarify the process and the flow of electrons in the cell. If you need further details or adjustments, feel free to ask!
