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CBSE Class 12 · Chemistry

Electrochemistry

Official NCERT chapter from Chemistry Part I–II (book code lech1). ExamMaster notes are original teaching at CBSE Class 12 depth.

This lesson follows the official chapter “Electrochemistry” in Chemistry Part I–II. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 12
  • Medium level
  • 8 concepts

1Electrochemical Cells

Electrochemical cells: a redox that makes or uses current as taught. Galvanic (voltaic) runs by itself and makes current; electrolytic is driven. A cell is two half-writes plus a circuit.

A single beaker with no path as “the cell” is a miss.

Figure. An electrochemical cell is either galvanic (chemical energy becomes electrical, spontaneous) or electrolytic (electrical energy drives a non-spontaneous change).

How it works

  1. Name galvanic versus electrolyticThe sort.
  2. Keep two halves and a circuitThe cell.
  3. Refuse a lone half as the wholeA pair.

2Galvanic Cells

Galvanic: oxidation at anode, reduction at cathode as taught; electrons through the wire. A Daniell-like Zn–Cu if named. Galvanic is a spontaneous redox-plus-wire.

Calling the cathode the oxidation-end is a swap.

Figure. Daniell cell while it discharges: oxidation at Zn frees electrons that travel the wire to Cu. The dashed salt bridge is the ionic return, not an electron path. Signs shown are for spontaneous discharge.

How it works

  1. Name anode=ox, cathode=redThe map.
  2. Keep the wire as the e− pathThe circuit.
  3. Refuse a forced-battery dump hereThat is electrolytic.

3Nernst Equation

Nernst: E = E° − (RT/nF) ln Q as taught (or the 0.059/n log form). Nernst adjusts E for non-standard Q. At equilibrium E=0 and Q=K. One 298 K write is enough.

Using E° as E at every Q is a miss.

Figure. Nernst at 298 K for n = 1: E = E° − 0.059 log Q with E° = 0.80 V. The line crosses E° when log Q = 0. Raising Q lowers E; the slope is −0.059 V per decade.

How it works

  1. Copy E°, n, and QThe given.
  2. Form the taught Nernst writeE.
  3. Keep log Q, not a sumThe caution.

Nernst hint

E°=1.10 V, n=2, Q=1 (standard). Find E.

  • ln Q0
  • E1.10 V
  • Readstandard so E=E°

Pro tip. Q=1 kills the log term.

4Conductance of Electrolytic Solutions

Conductance: κ and molar Λ as taught; Λ = κ / c (school units). Strong electrolytes sit high; weak sit low as framed. Conductance is an ion-flow look, not a cell-emf.

Using E as κ is a miss.

Figure. Kohlrausch for a strong electrolyte: Λm = Λm° − K√c. The intercept at √c = 0 is Λm° = 150 S cm² mol⁻¹; the line falls as √c rises. It does not pass through the origin.

How it works

  1. Name κ or ΛThe measure.
  2. Read strong/weak as high/low as taughtThe hint.
  3. Keep it a solution-lookNot emf.

5Electrolytic Cells and Electrolysis

Electrolytic cells and electrolysis: an outside voltage drives a non-spontaneous redox as taught. Faraday: mass tracks charge as framed. Electrolysis is a force-through, not a galvanic.

A Daniell cell labelled electrolysis because ions move is a miss.

Figure. An electrolytic cell is one vessel plus an external battery. Oxidation still sits at the anode, but that anode is now the positive terminal — the signs flip versus a discharging galvanic cell.

How it works

  1. Name an outside V and a forced redoxElectrolysis.
  2. Keep Faraday as mass-with-charge if askedThe extra.
  3. Refuse spontaneous as this headingThat was galvanic.

6Batteries

Batteries: a packaged galvanic as taught — primary (one-use) versus secondary (recharge) if split. A battery is a use-case of the cell, not a new law. One dry-cell or lead-store mention is enough.

A fuel-cell dump as the only battery is a skip of this heading’s pack.

Figure. A primary cell (dry cell) is discharged once. A secondary cell (lead–acid: Pb | H₂SO₄ | PbO₂) is the same redox run backwards on charge.

How it works

  1. Name primary or secondary as taughtThe sort.
  2. Keep it a packaged galvanicThe battery.
  3. Refuse a how-to rebuildSchool-size.

7Fuel Cells

Fuel cells: a galvanic that is fed fuel as taught (H2–O2 if named). Fuel cell is a continuous-feed, not a closed dry-cell. One school reaction-mention is enough.

A torch-battery labelled fuel cell because it “has energy” is a miss.

Figure. A hydrogen–oxygen fuel cell is a galvanic cell fed continuously. H₂ is oxidised at the anode, O₂ is reduced at the cathode, and the product that leaves is H₂O — not a stored solid electrode.

How it works

  1. Name a fed-fuel galvanicThe fuel cell.
  2. Keep H2–O2 as the case if taughtThe example.
  3. Refuse a closed dry-cell as this headingDifferent pack.

8Corrosion

Corrosion: a unwanted galvanic on a metal as taught — rust as the school case. Corrosion is a damage-redox, not a battery you wanted. Protection (coating, sacrificial) if named — a job-sentence, not a workshop-manual.

A rust-sticker with no anode/cathode-talk is a mute picture.

Figure. Rusting is a short-circuited galvanic cell on the same iron: anodic patches oxidise Fe to Fe²⁺, cathodic patches reduce O₂ in water, and electrons travel through the metal.

How it works

  1. Name the unwanted galvanicCorrosion.
  2. Keep rust as the caseThe look.
  3. Add a named protect only as taughtSchool-size.
In a galvanic cell, oxidation is at the
  1. Anode as taught
  2. Cathode
  3. Solvent

The map.

Notes

  • Mapped to the official NCERT chapter “Electrochemistry”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • E = E° − (RT/nF) ln Q
  • anode=ox, cathode=red (galvanic)

Recap

Hold these pegs from the official chapter “Electrochemistry”. The wording is ExamMaster’s teaching, not a textbook recap.

Electrochemical Cells
Electrochemical cells: a redox that makes or uses current as taught.
Galvanic Cells
Galvanic: oxidation at anode, reduction at cathode as taught; electrons through the wire.
Nernst Equation
Nernst: E = E° − (RT/nF) ln Q as taught (or the 0.059/n log form).
Conductance of Electrolytic Solutions
Conductance: κ and molar Λ as taught; Λ = κ / c (school units).
Electrolytic Cells and Electrolysis
Electrolytic cells and electrolysis: an outside voltage drives a non-spontaneous redox as taught.
Batteries
Batteries: a packaged galvanic as taught — primary (one-use) versus secondary (recharge) if split.

Practise Electrochemistry

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