Zadanie 3b
Wzorowane na: Chemistry SL Paper 2, May 2022, TZ2, pytanie 3(b). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 3a-3d.
Methanal, HCHO, is manufactured by passing methanol vapour over a silver catalyst at a high temperature.
CH3OH(g) ⇌ HCHO(g) + H2(g) ΔH = +92 kJ mol−1
Polecenie
(i) On the axes below, sketch Maxwell–Boltzmann energy distribution curves for the methanol molecules at two temperatures, T1 and T2, where T2 > T1.
(ii) Explain the effect of increasing the temperature on the equilibrium yield of methanal.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) both axes correctly labelled «x: kinetic energy / energy; y: number of molecules / fraction of molecules / probability density» ✔
the peak of the T2 curve is lower AND to the right of the peak of the T1 curve ✔
both curves start at the origin AND have the correct asymmetric shape AND the T2 curve finishes above the T1 curve ✔
(ii) the yield increases AND the equilibrium shifts to the right / favours the forward reaction ✔
the forward reaction is endothermic / ΔH is positive ✔
Schemat punktowania
(i) [1] each for labels, relative peak positions and shape of curves (curves must not touch the x-axis at high energy, must not cross at the origin). Do not accept «energy» alone for the label of the y-axis. (ii) M1: increase in yield with the shift to the products; M2: reason based on the endothermic forward reaction.