Zadanie 3a
Wzorowane na: Chemistry SL Paper 3, May 2024, TZ1, 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
Potassium bromide, KBr, forms a three-dimensional lattice of ions.
(i) Demonstrate how the electronegativity values and bonding triangle in sections 9 and 17 of the data booklet support an ionic model for this solid.
(ii) Outline the nature of the forces that hold the lattice together.
(iii) Outline why a crystal of potassium bromide shatters when it is struck sharply.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) electronegativity difference Δχ = 3.0 − 0.8 = 2.2 AND average electronegativity ✔
this point falls in the «ionic» region of the bonding triangle ✔
(ii) electrostatic attraction between oppositely charged ions ✔
(iii) a small displacement of a layer brings ions of the same charge next to each other ✔ «so they repel and the crystal cleaves»
Schemat punktowania
(i) M1: both values calculated; M2: located in the ionic region. Do not accept "ionic" without reference to the bonding triangle. (ii) Do not accept "ionic bonds". (iii) Do not accept "the bonds are weak".