Zadanie 3a
Wzorowane na: Chemistry SL Paper 2, 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
Sulfur dioxide, SO2, can be represented by more than one Lewis (electron dot) structure.
(i) Sketch a Lewis (electron dot) structure of SO2 in which all atoms obey the octet rule.
(ii) State the molecular geometry of SO2 and the O-S-O bond angle.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) 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 same structure with the double bond on the other oxygen
OR
the single S–O bond drawn as a coordination bond from S to O
(ii) molecular geometry: bent / V-shaped / angular ✔
bond angle: slightly less than 120° / any value from 115° to 119° «actual value 119°» ✔
Schemat punktowania
(i) [1] for any structure in which S and both O atoms have eight electrons; electron pairs may be dots, crosses or lines. A delocalized or dashed-bond structure is not accepted. (ii) M1: bent / V-shaped; M2: an angle below 120° but not far below it. Do not award M2 for 120° or for 109.5°.
Komentarz
Sulfur has three electron domains (two bonding, one non-bonding), so the electron domain geometry is trigonal planar and the lone pair squeezes the angle slightly below 120°.