Zadanie 4a
Wzorowane na: Chemistry HL Paper 2, November 2024, pytanie 4(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
Sulfur dioxide, SO2, can be represented by more than one Lewis (electron dot) structure.
(i) Sketch two different Lewis (electron dot) structures of SO2, one in which all atoms obey the octet rule and one in which sulfur does not.
(ii) State the criterion chemists use to choose the more stable of the Lewis structures.
(iii) Use section 11 of the data booklet to predict the length, in pm, of each sulfur-oxygen bond in SO2.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) obeys the octet rule: O=S−O with one lone pair on S, two lone pairs on the oxygen of the double bond and three lone pairs on the oxygen of the single bond «formal charges: S +1, single-bonded O −1» ✔
OR
the resonance structure with the double bond on the other oxygen
does not obey the octet rule: O=S=O with one lone pair on S and two lone pairs on each oxygen «S has ten electrons, all formal charges zero» ✔
(ii) «lowest» formal charges / formal charges closest to zero ✔
(iii) any value from 143 to 160 pm «S=O is 143 pm and S–O is 161 pm in the data booklet; actual value 143 pm» ✔
Schemat punktowania
(i) M1: structure that obeys the octet rule (accept resonance structures); M2: structure with an expanded octet on sulfur. Electron pairs may be shown as dots, crosses or lines. Structures drawn with partial or dashed bonds (resonance hybrids) are not accepted. (ii) [1]. (iii) [1] for a single value from 143 to 160 pm; no mark if different lengths are quoted for the two bonds. Part (iii) is marked independently of the structures drawn in (i).