October 04, 2022, 08:35:02 PM
Forum Rules: Read This Before Posting


Topic: Standard Electrode Potentials Internal Resistance  (Read 590 times)

0 Members and 1 Guest are viewing this topic.

Offline Uber-Dan

  • New Member
  • **
  • Posts: 4
  • Mole Snacks: +0/-0
Standard Electrode Potentials Internal Resistance
« on: April 08, 2022, 01:18:55 AM »
Hello all,
So I've been learning about standard electrode potentials in class. I know that they are measured under standard conditions, but I haven't been able to find any information on what internal resistance is considered "standard". There will obviously always be some, but do they just assume it is zero because the circuits they can design may as well have zero resistance?
Thanks in Advance

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27182
  • Mole Snacks: +1765/-406
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Standard Electrode Potentials Internal Resistance
« Reply #1 on: April 08, 2022, 02:54:52 AM »
Resistance is left undefined ("whatever the solution has"). It doesn't matter for potential measurements done without load.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline Uber-Dan

  • New Member
  • **
  • Posts: 4
  • Mole Snacks: +0/-0
Re: Standard Electrode Potentials Internal Resistance
« Reply #2 on: April 08, 2022, 05:26:12 AM »
So would any changes in resistance in a galvanic cell (for instance the resistance in the salt bridge) not affect the voltage, but the current instead?

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27182
  • Mole Snacks: +1765/-406
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Standard Electrode Potentials Internal Resistance
« Reply #3 on: April 08, 2022, 06:14:40 AM »
This is a bit more complicated. Do you know what an ohmic drop is?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline Uber-Dan

  • New Member
  • **
  • Posts: 4
  • Mole Snacks: +0/-0
Re: Standard Electrode Potentials Internal Resistance
« Reply #4 on: April 08, 2022, 07:01:47 AM »
No, but after a quick google search, it seems that it is the difference between the applied voltage and the actual voltage?

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27182
  • Mole Snacks: +1765/-406
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Standard Electrode Potentials Internal Resistance
« Reply #5 on: April 08, 2022, 11:54:34 AM »
Something like that, although "applied" and "actual" are just one of ways describing it. Broadly speaking when you have current i flowing through a resistance R, and you measure voltage on the contacts, it will be -iR. Ideal battery has no internal resistance, so it always produces the same voltage, but no practical battery is ideal, so they all behave as if their voltage was lower under load.

Knowing the internal battery resistance is necessary to estimate the measurement error of the voltage, but as typical digital voltmeter has internal resistance in the 10 MΩ range, and typical battery (like AA) has an internal resistance in the single Ω range, it rarely really matters.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Sponsored Links