Zadanie 8f
Wzorowane na: Chemistry HL Paper 2, May 2022, TZ2, pytanie 8(f). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 8a-8f.
Carbon occurs as several allotropes and forms an enormous variety of organic compounds.
Polecenie
Ethane reacts with iodine vapour.
C2H6(g) + I2(g) → C2H5I(g) + HI(g)
(i) Calculate the enthalpy change of the reaction, ΔH, using section 12 of the data booklet.
(ii) Draw and label an enthalpy level diagram for this reaction on the axes below.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) bond breaking: C–H + I–I = 414 + 151 = 565 «kJ» ✔
bond forming: C–I + H–I = 228 + 298 = 526 «kJ» ✔
«ΔH = bonds broken − bonds formed = 565 − 526 =» +39 «kJ mol−1» ✔
(ii) products drawn at a higher enthalpy than the reactants ✔
ΔH / +39 «kJ» labelled on an arrow from the reactants to the products
OR
activation energy / Ea labelled on an arrow from the reactants to the top of the curve ✔
Schemat punktowania
(i) Award [3] for the correct final answer. Award [2 max] for −39 kJ (reversed sign). (ii) M1: products above reactants (an endothermic profile); M2: ΔH or Ea labelled; both levels must be labelled with the species or with 'reactants' and 'products'.
Komentarz
For an endothermic reaction the products are drawn above the reactants and ΔH is positive.