P is ammonium iron(II) sulfate — it contains Fe²⁺, NH₄⁺ and SO₄²⁻.
Purple potassium manganate(VII) (Q) oxidises Fe²⁺ to Fe³⁺:
5Fe²⁺ + MnO₄⁻ + 8H⁺ → 5Fe²⁺… → 5Fe³⁺ + Mn²⁺ + 4H₂O
It is self-indicating: while Fe²⁺ remains, the purple is decolourised; the first drop of excess Q gives a pale pink that persists — the end-point. Because Q is dark, read the burette from the top of the meniscus.
Average titre 13.65 cm³ × 0.0200 mol/dm³ = 2.73×10⁻⁴ mol KMnO₄; ×5 = 1.365×10⁻³ mol Fe²⁺ in 25 cm³ → 0.0546 mol/dm³.
Try the 📈 Show curve button to see the redox titration curve (electrode potential vs volume) — a learning aid; it isn't part of the exam.