EasyChemistryHigh School (11–12)Electrochemistry › Galvanic Cells, Electrode Potential and the Nernst EquationNumericalConceptualA-LevelAPBoard ExamIB
A cell is written as Pt(s) mid Sn²⁺(aq), Sn⁴⁺(aq) ∥ Br⁻(aq) mid Br₂(l) mid Pt(s)…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cell is written as . The standard potentials are and . Write the half-reaction at each electrode and the overall reaction. Find the number of moles of electrons in the equation and the standard emf of the cell.
Need a reminder? The key ideaShow
The emf of a cell is the potential difference between its electrodes when no current flows. . In the cell line, the left electrode is the anode (oxidation) and the right electrode is the cathode (reduction). Under load, .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The anode. The left electrode holds tin(II) and tin(IV) ions. Tin(II) is oxidised: .
Step 2. The cathode. Bromine is reduced: .
Step 3. The cell reaction. The electrons already balance. , with .
Step 4. The emf. .
Answer: of electrons and . The platinum electrodes only carry electrons, because neither couple has a solid metal.
Check. The value is positive, so the cell runs as it is written.
Discussion (0)
Log in to join the discussion.
Loading…