Galvanic Cell EMFJEE Main

Standard cell potential & spontaneity — interactive Chemistry simulation for IIT-JEE.

Concept

A galvanic (voltaic) cell turns a spontaneous redox reaction into electricity. The electrode with the higher reduction potential is reduced (the cathode); the other is oxidised (the anode). Their difference is the standard cell EMF.

Key formula

E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}, \qquad \Delta G^\circ = -nFE^\circ_{cell}

Derivation

Each half-cell has a standard reduction potential vs the hydrogen electrode. Subtracting the anode's value from the cathode's gives $E^\circ_{cell}$ — for the Daniell cell (Zn|Cu), $0.34 - (-0.76) = 1.10\ \text{V}$ .

A positive EMF means $\Delta G^\circ = -nFE^\circ_{cell} < 0$ , so the reaction is spontaneous and drives current through the external circuit.

Scenarios to explore

Galvanic Cell EMF — Standard cell potential, ΔG° and spontaneity.

Real-world applications

Batteries and fuel cells.
Corrosion prediction and prevention (sacrificial anodes).
Electroplating and electrorefining.

JEE exam tips

Cathode = reduction = higher E°; anode = oxidation = lower E°.
Positive $E^\circ_{cell}$ ⇔ negative $\Delta G^\circ$ ⇔ spontaneous.
Cell notation: anode | anode ion || cathode ion | cathode.

Common mistakes

Adding the two potentials instead of subtracting.
Reversing the sign of the anode potential incorrectly.
Picking the wrong electrode as cathode (it is the higher reduction potential).

Exam traps to avoid

$E^\circ$ values are intensive — do not multiply them by stoichiometric coefficients.
A larger EMF does not mean a faster reaction, only a more spontaneous one.