SKH Thermodynamics Labs

Lab 13 · Electrochemistry

Why does the cell voltage change?

Predict the voltage, change the concentrations, and check your result.

2027 prototype
Help review this design

Choose a caseValues load into the two solutions below.

Set the two solutions

298.15 K

Each compartment contains a metal electrode M(s) and dissolved M²⁺ ions.

Left solution
mol/L

Activity aL —

Right solution
mol/L

Activity aR —

Calculate the cell to identify the favored direction.

Activity coefficients and model assumptions

Activities use a = γc/c°. The standard concentration c° is 1 mol/L. The supplied coefficients are assumptions for this teaching example.

Both standard reduction potentials use the same hypothetical reference and equal 0 V at 298.15 K. Two electrons transfer per reaction as written. Pure metal is present in each compartment, with activity 1. The model uses a zero liquid-junction potential and predicts reversible cell potential.

Individual-ion activities depend on the chosen convention. Bulk solutions must be electroneutral. The supplied γ values are teaching inputs.

Open the general cell builder for other half-reactions and standard-state inputs.

More concentration experiments

Compare a smaller concentration ratio, then compare the same ratio at lower concentrations.

Read and check the result

Make a prediction, then calculate the cell.

The sign refers to left oxidation and right reduction in the written cell reaction.

Compare your cases

Saved rows keep their original inputs.

Calculate a case and add its result here. Then change the concentrations and compare.

What changed? Which calculation supports your explanation? For equal activities, check whether Q = K and E = 0.

Your inputs, comparisons and explanation are kept in this open page. Download the study to keep a copy and reopen it later.