Electrochemistry: Write Shorthand Cell Notation
Question
Write cell shorthand notation for the following cell reaction:
[latex]2\mathrm{Ag}^+\mathrm{(aq)}+\mathrm{Cu}\,\mathrm{(s)}\longrightarrow\mathrm{Cu}^{2+}\mathrm{(aq)}+2\mathrm{Ag}\,\mathrm{(s)}[/latex]
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Cu (s)│Cu2+(aq)║Ag+(aq)│Ag (s)
Refer to Section 9.2: Galvanic Cells (1).
Strategy Map
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1. Identify which species in the overall reaction takes part in the reduction half-reaction.
Show/Hide HintReduction is when a species gains electrons (the product species is more negatively charged than the reactant species) |
2. Identify which species in the overall reaction takes part in the oxidation half-reaction.
Show/Hide HintOxidation is when a species loses electrons (the product species is more positively charged than the reactant species). |
3. Write out the 2 half-reactions.
Show/Hide HintUse electrons to balance out the total charge between the reactant and product sides of the half-reaction equations. Electrons are reactants when they are gained in a reduction. Electrons are products when they are gained in an oxidation. |
4. Translate the information to the shorthand notation.
Show/Hide HintFrom left to right, the short-hand notation displays the oxidation half-reaction details, then the reduction half-reaction details. The format follows the path of the electron from the electrode at the anode to the electrode at the cathode. Separate each species in the half reactions with a [ , ] comma (same physical state) or a [ | ] single vertical line (different physical state). The salt bridge that separates the anode and cathode in the galvanic cells is represented by a [ || ] double vertical line. The complete correct answer includes the physical states and charges but does not include stoichiometric coefficients. Example format: |
Solution
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[latex]\textcolor{#ff0000}{2\mathrm{Ag}^+\mathrm{(aq)}}+\textcolor{#0000ff}{\mathrm{Cu}\,\mathrm{(s)}}\longrightarrow\textcolor{#0000ff}{\mathrm{Cu}^{2+}\mathrm{(aq)}}+\textcolor{#ff0000}{2\mathrm{Ag}\,\mathrm{(s)}}[/latex]
Oxidation at anode
Reduction at cathode
[latex]\textcolor{#0000ff}{\mathrm{Cu}\,\mathrm{(s)}}\longrightarrow\textcolor{#0000ff}{\mathrm{Cu}^{2+}\mathrm{(aq)}}+2\mathrm{e}^-[/latex]
[latex](\textcolor{#ff0000}{\mathrm{Ag}^+\mathrm{(aq)}}+\mathrm{e}^-\longrightarrow\textcolor{#ff0000}{\mathrm{Ag}\,\mathrm{(s)}})\times2[/latex]
Anode (s)│Anode (aq)║Cathode (aq)│Cathode (s)
Answer: Cu (s)│Cu2+(aq)║Ag+(aq)│Ag (s)
Guided Solution
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The guided solution below will give you the reasoning for each step to get your answer, with reminders and hints.
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This question is a theory type problem where you will demonstrate your skills of turning a reaction into its shorthand notation.
Show/Hide ResourceRefer to Section 9.2: Galvanic Cells (1). |
Shorthand notation is a used to describe a redox reaction in its simplest form. It shows the pathway of electron flow without needing to draw a diagram. In shorthand notation, the electron will flow left to right from the anode to the cathode.
Show/Hide Think About This!
Ensure you to include all phases as well as any charges. Stoichiometry is not included. |
Recall the shorthand notation template.
Show/Hide Don’t Forget!Anode reactant | Anode product ║ Cathode reactant | Cathode product Or, in this case: Anode (s)│Anode (aq) ║ Cathode (aq)│Cathode (s) |
The anode is the negatively charged electrode where oxidation occurs. The cathode is the positively charged electrode where the reduction occurs. The electrons will flow from the negatively charged anode to the positively charged cathode
Show/Hide Don’t Forget!Remember these by thinking “An-Ox (anode-oxidation) and “Red-Cat” (reduction-cathode). |
Identify which reactant was oxidized and which was reduced:
Show/Hide Don’t Forget!The reactant being oxidized will lose an electron(s) and its product will gain a positive charge. The reactant being reduced will gain an electron(s) and its product will gain a negative charge. Remember this by thinking the phrase “LEO says GER” (lose-electrons-oxidized) and (gains-electrons-reduced). Show/Hide Watch Out!
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| Write out the half reactions first; recall what a half reaction is.
Oxidation half reaction: [latex]\mathrm{Cu}\,\mathrm{(s)}\longrightarrow\mathrm{Cu}^{2+}\mathrm{(aq)}+2\mathrm{e}^-[/latex] Reduction half reaction: [latex](\mathrm{Ag}^+\mathrm{(aq)}+\mathrm{e}^-\longrightarrow\mathrm{Ag}\,\mathrm{(s)})\times2[/latex]
Show/Hide Think About This!
Note: Stoichiometry is not included in shorthand notation. |
| Translate the half-reaction information into the short-hand notation format:
Cu (s)│Cu2+(aq)║Ag+(aq)│Ag (s) |
| Complete Solution |
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| From the provided overall re-dox reaction:
[latex]2\mathrm{Ag}^+\mathrm{(aq)}+\mathrm{Cu}\,\mathrm{(s)}\longrightarrow\mathrm{Cu}^{2+}\mathrm{(aq)}+2\mathrm{Ag}\,\mathrm{(s)}[/latex] Identify the species participating in oxidation and reduction half-reactions: [latex]\mathrm{Ag}^+\mathrm{(aq)}\longrightarrow\mathrm{Ag}\,\mathrm{(s)}[/latex] Silver is becoming more negatively charged; therefore, 1 electron was gained by the reactant Ag+ (aq). Gaining Electrons is Reduction (GER) [latex]\mathrm{Cu}\,\mathrm{(s)}\longrightarrow\mathrm{Cu}^{2+}\mathrm{(aq)}[/latex] Copper is becoming more positively charged; therefore, 2 electrons were lost by the reactant Cu(s). Losing Electrons is Oxidation (LEO) |
| Add electrons to the reactant or product sides to balance the charges of the half-reactions:
[latex]\mathrm{Ag}^+\mathrm{(aq)}+\mathrm{e}^-\longrightarrow\mathrm{Ag}\,\mathrm{(s)}[/latex] Gained electrons are reactants. [latex]\mathrm{Cu}\,\mathrm{(s)}\longrightarrow\mathrm{Cu}^{2+}\mathrm{(aq)}+2\mathrm{e}^-[/latex] Lost electrons are products. |
| Translate the details into the short-hand notation format:
Anode (s)│Anode (aq)║Cathode (aq)│Cathode (s) Answer: Cu (s)│Cu2+(aq)║Ag+(aq)│Ag (s) |
Check Your Work
Make sure that all the necessary components are present in the final shorthand notation, including:
- A salt bridge [ || ] — 2 vertical lines separating the anode and cathode half-reaction details
- Oxidation half-reaction details on the left-hand side
- Reduction half-reaction details on the right-hand side
- Solid electrode species on the far left and far right sides of the short-hand notation. If there is no solid species, check the question details for inert electrode information (e.g., platinum or graphite)
- Separation of each species with a [ , ] comma (same physical state) or a [ | ] single vertical line (different physical state)
- Inclusion of physical states (i.e., solid, liquid, gas, or aqueous)
- No stoichiometric coefficients
Refer to:
Does your answer make chemical sense?
Show/Hide Answer
This answer makes sense because we know that the shorthand notation follows the flow of electrons. The anode is negatively charged, and the cathode is positively charged. Electrons themselves are negatively charged, so they are repulsed by the anode and attracted to the cathode. Electrons at the anode act like a compressed spring with stored potential energy. If the reduction potential at the cathode is greater than the anode, the electron will flow spontaneously.
PASS Attribution
- LibreTexts TRU: Fundamentals and Principles of Chemistry (CHEM 1510 and CHEM 1520) (3)
- Question 9.E.3 (b) from LibreTexts TRU: Fundamentals and Principles of Chemistry (CHEM 1510 and CHEM 1520) (4) is adapted under a CC BY-NC-SA 4.0 license.
- Question 9.E.3 (b) is question Q11 /VC (b) from LibreTexts Chem 1202 (5), which is under a CC BY-NC-SA 4.0 license.
- Q11 (b) is question 11 (b) from OpenStax Chemistry 2e (6), which is under a CC BY-NC-SA 4.0 license.
References
1. OpenStax. 9.2: Galvanic Cells. In TRU: Fundamentals and Principles of Chemistry (CHEM 1510 and CHEM 1520); LibreTexts, 2022. https://chem.libretexts.org/Courses/Thompson_Rivers_University/TRU%3A_Fundamentals_and_Principles_of_Chemistry_(CHEM_1510_and_CHEM_1520)/09%3A_Electrochemistry/9.02%3A_Galvanic_Cells.
2. OpenStax. 9.1: Balancing Oxidation-Reduction Reactions. In TRU: Fundamentals and Principles of Chemistry (CHEM 1510 and CHEM 1520); LibreTexts, 2022. https://chem.libretexts.org/Courses/Thompson_Rivers_University/TRU%3A_Fundamentals_and_Principles_of_Chemistry_(CHEM_1510_and_CHEM_1520)/09%3A_Electrochemistry/9.01%3A_Balancing_Oxidation-Reduction_Reactions.
3. Thompson Rivers University. TRU: Fundamentals and Principles of Chemistry (CHEM 1510 and CHEM 1520); LibreTexts, 2024. https://chem.libretexts.org/Courses/Thompson_Rivers_University/TRU%3A_Fundamentals_and_Principles_of_Chemistry_(CHEM_1510_and_CHEM_1520).
4. Thompson Rivers University. 9.E: Exercises on Electrochemistry. In TRU: Fundamentals and Principles of Chemistry (CHEM 1510 and CHEM 1520); LibreTexts, 2022. https://chem.libretexts.org/Courses/Thompson_Rivers_University/TRU%3A_Fundamentals_and_Principles_of_Chemistry_(CHEM_1510_and_CHEM_1520)/09%3A_Electrochemistry/9.E%3A_Exercises_on_Electrochemistry.
5. Mount Royal University. 6.9 Exercises on Electrochemistry. In Chem 1202; LibreTexts, 2021. https://chem.libretexts.org/Courses/Mount_Royal_University/Chem_1202/Unit_6%3A_Electrochemistry/6.9%3A_Exercises_on_Electrochemistry.
6. Flowers, P.; Theopold, K.; Langley, R.; Robinson, W. R. 17.1 Review of Redox Chemistry. In Chemistry 2e; OpenStax, 2019. https://openstax.org/books/chemistry-2e/pages/17-exercises.
