Calculate Ecell for The Following Reaction at 25 C

The standard cell potential (Ecell) is a measure of the voltage produced by a galvanic cell under standard conditions. This calculator helps you determine Ecell for a given redox reaction at 25°C using the Nernst equation.

What is Ecell?

The standard cell potential (Ecell) represents the maximum electrical potential difference between the anode and cathode in a galvanic cell when all reactants and products are in their standard states (1 M concentration for solutes, 1 atm pressure for gases, and pure solids or liquids).

Ecell is crucial in electrochemistry as it determines the spontaneity of redox reactions. A positive Ecell indicates a spontaneous reaction, while a negative value means the reaction is non-spontaneous as written.

Note: Ecell values are temperature-dependent. This calculator uses standard conditions at 25°C (298.15 K).

How to Calculate Ecell

The standard cell potential is calculated using the Nernst equation:

Ecell = E°cell - (RT/nF) * ln(Q)

Where:

E°cell = Standard cell potential (V)
R = Universal gas constant (8.314 J/mol·K)
T = Temperature in Kelvin (298.15 K at 25°C)
n = Number of electrons transferred in the balanced redox reaction
F = Faraday constant (96,485 C/mol)
Q = Reaction quotient

For standard conditions, Q = 1, so the equation simplifies to Ecell = E°cell.

Example Calculation

Consider the reaction:

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Given:

E°cell = 1.10 V
n = 2 electrons
Q = 1 (standard conditions)

Calculation:

Ecell = 1.10 V - (0.0257 V) * ln(1) = 1.10 V

The calculated Ecell is 1.10 V, indicating the reaction is spontaneous under standard conditions.

FAQ

What is the difference between E°cell and Ecell?

E°cell is the standard cell potential under standard conditions (1 M, 1 atm, pure solids/liquids). Ecell is the actual cell potential under non-standard conditions, calculated using the Nernst equation.

Why is temperature important in Ecell calculations?

The Nernst equation includes temperature because the reaction quotient (Q) depends on temperature. At 25°C, we use 298.15 K as the standard temperature.

Can Ecell be negative?

Yes, a negative Ecell indicates the reaction is non-spontaneous as written. The sign tells you whether the reaction will occur spontaneously under the given conditions.