Zadanie 1b
Wzorowane na: Chemistry SL Paper 2, November 2024, pytanie 1(b). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
Ethane reacts with bromine gas, Br2(g), in the presence of UV light to form bromoethane.
(i) State the type of this reaction and the name of its mechanism.
(ii) Explain the mechanism of this reaction by writing equations for one initiation step, two propagation steps and one termination step.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) substitution AND «free-»radical ✔
(ii) initiation: Br2 → 2 Br ∙ ✔
propagation: C2H6 + Br ∙ → C2H5 ∙ + HBr ✔
C2H5 ∙ + Br2 → C2H5Br + Br ∙ ✔
termination (any one of): C2H5 ∙ + C2H5 ∙ → C4H10
OR
C2H5 ∙ + Br ∙ → C2H5Br
OR
Br ∙ + Br ∙ → Br2 ✔
Schemat punktowania
(i) [1] for both: substitution AND free-radical; accept radical substitution. (ii) M1: initiation step; M2: first propagation step; M3: second propagation step; M4: termination step. The unpaired electron must be shown on every radical (a dot); ignore state symbols; accept "UV" written above the arrow. The two propagation steps must each have one radical on both sides; M2 and M3 may be given in either order. Award no mark for a step that is not balanced.