How does concentration change a cell's voltage?
"How does concentration change a cell's voltage?" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the lesson "The Nernst equation" in Electrochemistry. Zinc gives up electrons on the left, Cu²⁺ takes them on the right. Change either concentration and read the voltmeter. The graph plots the voltage against log Q, where Q = [Zn²⁺]/[Cu²⁺]. E = E° − (0.059/n) log Q at 298 K. Q = [Zn²⁺]/[Cu²⁺] here, products over reactants. Each tenfold change in Q moves E by 0.059/n V, and E = 0 when Q = K. JEE Main asked 46 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson The Nernst equation in Electrochemistry. Change the values and watch what happens.
In JEE Main
42 shifts analysed
46 questions from Electrochemistry across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT §2.3
- For Mⁿ⁺(aq) + ne⁻ → M(s), the potential at a general concentration is E = E° − (RT/nF) ln(1/[Mⁿ⁺]), since a pure solid is taken as unity. R = 8.314 J K⁻¹ mol⁻¹, F = 96487 C mol⁻¹, T in kelvin.
- For the Daniell cell, E_cell = E°_cell − (RT/2F) ln([Zn²⁺]/[Cu²⁺]). The cell voltage rises when [Cu²⁺] is raised or [Zn²⁺] lowered.
- At 298 K, with base-10 logs, RT/F × 2.303 = 0.059 V, so E_cell = E°_cell − (0.059/n) log Q.
- For aA + bB + ne⁻ → cC + dD, Q = [C]^c[D]^d/[A]^a[B]^b, with pure solids and liquids left out. Use the same n for both electrodes: for Ni(s) + 2Ag⁺ → Ni²⁺ + 2Ag(s), n = 2 and Q = [Ni²⁺]/[Ag⁺]².
- Worked: Mg|Mg²⁺(0.130 M)||Ag⁺(0.0001 M)|Ag with E° = 3.17 V gives E = 3.17 − (0.059/2) log(0.130/10⁻⁸) = 3.17 − 0.21 = 2.96 V.
- A hydrogen electrode in a solution of pH 10 (at 1 bar H₂): E = −0.059 × pH = −0.59 V.
Questions
3 answers
- What does the "How does concentration change a cell's voltage?" simulation show?
- Zinc gives up electrons on the left, Cu²⁺ takes them on the right. Change either concentration and read the voltmeter. The graph plots the voltage against log Q, where Q = [Zn²⁺]/[Cu²⁺].
- Does JEE Main ask questions from Electrochemistry?
- Yes. JEE Main asked 46 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "The Nernst equation" in Electrochemistry (Class 12 Chemistry).
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