Zadanie 21c
Wzorowane na: Chemistry HL Paper 3, May 2023, TZ1, pytanie 21(c). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
A detector tube for propan-2-ol vapour in workplace air contains orange dichromate ions, which turn green as they are reduced to chromium(III) ions.
Cr2O72−(aq) + 14 H+(aq) + 6 e− → 2 Cr3+(aq) + 7 H2O(l)
Deduce the half-equation for the oxidation of propan-2-ol and the overall redox equation for the reaction in the tube.
Half-equation for the oxidation of propan-2-ol:
Overall equation:
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
Half-equation: CH3CH(OH)CH3 → CH3COCH3 + 2 H+ + 2 e− ✔
Overall: 3 CH3CH(OH)CH3 + Cr2O72− + 8 H+ → 3 CH3COCH3 + 2 Cr3+ + 7 H2O ✔
Schemat punktowania
M1: half-equation with propanone as the product, balanced for atoms and charge. M2: overall equation with the electrons cancelled. Accept C3H8O and C3H6O as formulas. Accept ECF for M2 from a wrong half-equation if the electrons are cancelled correctly.