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Nernst equation explorer

Run the Nernst Equation Explorer fullscreen
Edit the MicroSim in the p5.js editor

About this MicroSim

The explorer combines a stylized galvanic cell diagram with a live Nernst calculator. Choose a reaction preset (Zn-Cu, Fe-Cu, concentration cell) or define custom \(E0\) and \(n\) values, then drag the oxidized and reduced concentration sliders (0.001-2.000 M). The voltmeter, electron flow arrows, and color-coded readout respond immediately, while the computation panel shows \(Q\), \(\,\log Q\), the substituted Nernst equation, and \(\Delta G = -nFE\) in kJ/mol. A mini graph traces the linear relationship between \(E\) and \(\log Q\), highlighting the current operating point.

How to use

  1. Pick a reaction from the dropdown. Presets auto-fill \(E0\) and \(n\), but you can adjust them; the Custom option reveals text inputs for electrode labels and potentials.
  2. Drag the Standard potential (E0) slider to explore hypothetical cells (range -1.50 to +1.50 V).
  3. Set the Electrons transferred (n) slider (1-4) to match the balanced reaction.
  4. Adjust the Oxidized concentration (anode) and Reduced concentration (cathode) sliders (0.001-2.000 M). These values feed \(Q = [\text{ox}]^a/[\text{red}]^b\).
  5. Read the dynamic outputs: voltmeter color (green for \(E>0\), red for \(E<0\)), full Nernst calculation, \(Q\) and \(\log Q\), and the plotted point on the \(E\) vs \(\log Q\) line.

Learning goals (Step 1)

Item Details
Subject area Chemistry - electrochemistry
Grade band AP Chemistry / introductory college
Learning objective Students will apply the Nernst equation to predict cell potentials at non-standard concentrations and explain how \(Q\) and \(n\) influence \(E\).
Bloom's level Apply
Duration 12-15 minutes
Prerequisites Balanced redox reactions, cell notation, equilibrium expressions, \(\log\) rules
Assessment ideas Learners capture two scenarios (spontaneous vs non-spontaneous) and justify the sign of \(E\) via \(Q\); quick-write comparing how doubling \(n\) changes the slope in \(E\) vs \(\log Q\).

Instructional design review (Step 1.5)

Question Target Decision
Single learning objective? Yes Focused on linking Nernst math to cell behavior.
Number of controls 1-5 Five rows (dropdown + two sliders + two more sliders) stay within limits.
Progressive disclosure Needed Custom text inputs appear only when Custom is selected; warning color only when \(E \le 0\).
Cognitive load Managed Diagram occupies upper half; calculations and graph share the lower half with clear headings.
Accessibility Required Controls live below the canvas with >=16 px fonts, high-contrast readouts, and descriptive labels.

Control inventory

# Control type Label text Value format Row
1 Dropdown + conditional inputs Reaction selector / custom electrode fields Dropdown with optional text/number inputs 1
2 Slider Standard potential (E0, V) -1.50 to +1.50 V, step 0.01 2
3 Slider Electrons transferred (n) 1-4 (integer) 3
4 Slider Oxidized concentration (M) 0.001-2.000 M, step 0.001 4
5 Slider Reduced concentration (M) 0.001-2.000 M, step 0.001 5

Layout planning (Step 2.5)

  • Number of control rows: 5
  • controlHeight = (5 x 60) + 40 = 340 px
  • drawHeight = 600 px (diagram + voltmeter + equation/graph region)
  • canvasHeight = 600 + 340 = 940 px
  • iframeHeight = 940 + 2 = 942 px
  • sliderLeftMargin = 240 px (150 px label + 90 px value buffer)
  • margin = 28 px

Position assignments

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// Row 1 (reaction selector + custom inputs)
controlRows[0].position(margin, drawHeight + 25);
// Row 2 (standard potential slider)
controlRows[1].position(margin, drawHeight + 95);
// Row 3 (n slider)
controlRows[2].position(margin, drawHeight + 165);
// Row 4 (oxidized concentration slider)
controlRows[3].position(margin, drawHeight + 235);
// Row 5 (reduced concentration slider)
controlRows[4].position(margin, drawHeight + 305);

Label/value alignment

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labelSpan.style('width', '150px');
valueSpan.style('width', '90px');
slot.style('width', '320px'); // slider widths expand dynamically via code

Lesson plan

  1. Demo (4 min): Instructor toggles between Zn-Cu and the concentration cell to illustrate how \(Q\) shifts \(E\) even when \(E0 = 0\).
  2. Slider lab (7 min): Students aim for \(E = 0\) by tuning concentrations, then record the \(Q\) value and explain the physical meaning (equilibrium).
  3. Graph link (4 min): Learners compare slopes when \(n=1\) vs \(n=3\) and note how the \(E\) vs \(\log Q\) line steepens or flattens.

References

  1. Atkins & de Paula. Physical Chemistry, 11th ed., Oxford University Press, 2017 - Derivation and interpretation of the Nernst equation.
  2. Housecroft & Sharpe. Inorganic Chemistry, 4th ed., Pearson, 2012 - Concentration cells and \(Q\) expressions in electrochemistry.