Ch 2Electrochemistry — Class 12 Chemistry, concept-first.

Objectives After studying this chapter, you should be able to: - describe what an electrochemical cell is, and tell a galvanic cell apart from an electrolytic cell; - apply the Nernst equation to find…

A redox reaction always has an oxidation half and a reduction half, and if those two halves are forced to happen in separate compartments — connected only by a wire and a salt bridge — the electron tr…

A galvanic cell is an electrochemical cell that converts the chemical energy of a spontaneous redox reaction directly into electrical energy.

The potential of an individual half-cell, by itself, cannot be measured. Only the difference between two half-cell potentials can be measured — and that difference is exactly the emf of the cell they…

Every standard electrode potential listed in Table 2.1 is measured with all species at unit concentration (1 M for ions in solution, 1 bar for gases) and 298 K.

Consider the Daniell cell with its circuit closed, driving the reaction

The electrical work obtainable from a cell in one second equals the potential multiplied by the charge that flows.

Before we can talk about how well an electrolyte solution conducts electricity, we need a few terms carried over from the physics of resistance.

An unknown resistance can ordinarily be measured very accurately on a Wheatstone bridge. Trying to use this directly on an ionic solution, however, runs into two difficulties:

Both conductivity and molar conductivity change as the concentration of an electrolyte changes. Conductivity always decreases with dilution, for weak and strong electrolytes alike — this is simply bec…

A galvanic cell lets a spontaneous redox reaction generate electricity on its own. An electrolytic cell works the other way round: an external DC source is connected across two electrodes, and the ele…

What actually comes out at the two electrodes during electrolysis depends on two things: the nature of the material being electrolysed, and the type of electrode used.

A battery is a practical, everyday source of electrical energy built from one or more galvanic cells joined in series.

In a primary battery, the cell reaction occurs only once — after the reactants are used up over time, the battery is dead and cannot be revived.

A secondary battery differs from a primary one in that it can be recharged: once discharged, passing a current back through the cell in the reverse direction restores the original reactants, so the ba…

Ordinary thermal power plants are not a very efficient way to generate electricity, and they pollute heavily.

Corrosion is the slow, spontaneous eating away of a metal's surface by the formation of oxides or other salts of that metal.

Fossil fuels like coal, oil, and gas power most of the world today, but burning them releases carbon dioxide, which traps heat and drives climate change — melting polar ice, raising sea levels, and th…

- Electrochemical cells convert chemical energy to electrical (galvanic) or vice versa (electrolytic).

These are the final answers printed at the end of the NCERT chapter. The book gives answers for some intext questions only — every question below links to our complete worked solution.

Higher-order thinking / exemplar-style practice problems.

Sample papers and previous-year board questions for this subject.