Zadanie 3a
Wzorowane na: Chemistry HL Paper 3, November 2024, pytanie 3(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
Chromium(III) oxide, Cr2O3, is a hard ceramic used as an abrasive and as a wear-resistant coating. Outline the bonding in chromium(III) oxide and its electrical conductivity in the solid state. Use sections 9 and 17 of the data booklet.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
Δχ = 3.4 − 1.7 = 1.7 AND average χ = (3.4 + 1.7)/2 = 2.55 ✔
ionic AND polar covalent «the point is in the polar covalent region, with a substantial ionic contribution; the percentage scale indicates comparable ionic and covalent character» ✔
non-conductor / insulator / poor conductor «no delocalized electrons and the ions cannot move» ✔
Schemat punktowania
M1: both values, with some working or in the correct range (average 2.5 to 2.6 accepted). M2: both bonding types are needed. M3: accept 'poor conductor'; do not accept 'conducts when molten' alone.
Komentarz
The point (2.55, 1.7) lies on the boundary between the ionic and polar covalent regions, so both descriptions are correct.