Zadanie 6a
Wzorowane na: Chemistry HL Paper 2, May 2022, TZ1, pytanie 6(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
Ozone, O3, is an allotrope of oxygen found in the upper atmosphere.
(i) Complete the boxes with arrows to show the ground-state electron configuration of an oxygen atom.
(ii) Deduce a Lewis (electron dot) structure of O3 in which every atom has an octet, and show any formal charges that are not zero.
(iii) Explain how the lengths of the two O-O bonds in ozone compare. Use section 11 of the data booklet.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) 2p: one pair of arrows «↑↓» in one box AND one arrow in each of the other two boxes ✔
2s: ↑↓ AND 1s: ↑↓
(ii) central O bonded to one terminal O by a double bond and to the other terminal O by a single bond; central O has one lone pair, the doubly bonded O has two lone pairs and the singly bonded O has three lone pairs ✔
formal charges: +1 on the central O AND −1 on the singly bonded terminal O «the doubly bonded O is 0» ✔
(iii) any three of:
the two O−O bonds are the same length ✔
resonance / delocalization of electrons «over the three oxygen atoms» ✔
bond order 1½ for both bonds ✔
length between that of an O−O single bond «148 pm» and an O=O double bond «121 pm» ✔
Schemat punktowania
(i) [1]; the two unpaired 2p arrows must be parallel (both up or both down); accept half arrows. (ii) M1: bonds and lone pairs correct; M2: formal charges correct. Accept dots, crosses or lines for electron pairs. A drawing with delocalized bonds instead of a single Lewis structure is not accepted. If the Lewis structure is wrong, allow ECF for the formal charges that follow from it. (iii) [1] each, maximum [3]. If the argument is about bond strength rather than bond length, award [2] at most.