Zadanie 3a
Wzorowane na: Chemistry HL Paper 1B, May 2026, TZ2, pytanie 3(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 3a-3f.
A titration was performed to find the concentration of iron(II) ions in a solution made from iron tablets. Portions of 25.00 cm3 of the iron(II) solution were acidified with excess dilute sulfuric acid and titrated with potassium manganate(VII) solution, which acts as its own indicator.
MnO4−(aq) + 5 Fe2+(aq) + 8 H+(aq) → Mn2+(aq) + 5 Fe3+(aq) + 4 H2O(l)
A standard 0.0200 mol dm−3 potassium manganate(VII) solution was used in a preliminary trial. The volume of titrant required was less than 5 cm3, so the standard solution was diluted before the main titrations.
Polecenie
Outline why a standard solution of potassium manganate(VII) was needed for this analysis.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
its concentration is accurately/precisely known, so the amount of MnO4− that reacted can be calculated from the volume added ✔
Schemat punktowania
[1] for the idea that the concentration is known precisely. 'It is pure' or 'it is stable' is not enough.