Voltmeter values drop w/ time when measuring elec chem cell?

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Discussion Overview

The discussion centers around the observation of decreasing voltage over time in a zinc-copper electrochemical cell set up in lemon juice. Participants explore the reasons behind this phenomenon, including the effects of the voltmeter and the nature of the electrochemical cell.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Mary describes her setup and notes that the voltage measured by the voltmeter decreases over time.
  • One participant questions the duration of the measurement process and mentions that the voltmeter draws current, which could affect the readings.
  • Another participant references "electrochemical cell polarization" as a potential explanation for the observed behavior, suggesting it is a normal occurrence for homemade cells.
  • A later reply reiterates the point about polarization and suggests that using copper sulfate solution instead of lemon juice could improve cell performance, while also cautioning about the toxicity of copper sulfate.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the exact cause of the voltage drop, but there is agreement that the phenomenon is normal for homemade electrochemical cells. Multiple perspectives on the contributing factors are presented.

Contextual Notes

There are limitations regarding the assumptions made about the voltmeter's impact and the specific conditions of the electrochemical cell, which may not be fully explored in the discussion.

Who May Find This Useful

Individuals interested in electrochemistry, experimental setups involving electrochemical cells, and those exploring the effects of measurement tools on experimental results may find this discussion relevant.

mizzmarymary
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I set up a zinc-copper elctrochemical cell by placing both electrodes in lemon juice to test the ability of lemon juice to conduct a current. I used a voltmeter and attached each lead to one of the metal electrodes. What I observed was that the voltage over time given on the voltmeter began to decrease and continued to decrease. I would be grateful if someone could explain what is happening? Thanks so much!
Mary
 
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How long did the process take?
The voltmeter draws some current and the cell does not run forever.
 
See "electrochemical cell polarization".
What you see is normal for these home made cells.
 
nasu said:
See "electrochemical cell polarization".
What you see is normal for these home made cells.
These cells work better if you use copper sulfate solution instead of the lemon juice. Careful, it is toxic.
 

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