Zadanie 2f
Wzorowane na: Chemistry HL Paper 2, November 2023, TZ2, pytanie 2(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 2a-2g.
Methanol, a possible fuel and chemical feedstock, can be produced by the hydrogenation of carbon dioxide according to the equilibrium
CO2(g) + 3 H2(g) ⇌ CH3OH(g) + H2O(g)
Polecenie
The conversion of carbon dioxide to methanol is usually carried out over a catalyst containing copper and zinc oxide.
(i) Sketch energy profiles for the forward reaction, with and without the catalyst, on the axes shown. Label ΔH and the two activation energies. Use your answer to part 2c(i).
(ii) State one change, other than adding a catalyst or raising the temperature, that would increase the rate of the forward reaction.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) two curves, each rising to a single peak AND ending at the same level «below that of the reactants» ✔
exothermic enthalpy change, ΔH, labelled «downward arrow between the reactant and product levels» ✔
both activation energies correctly labelled «from the reactant level to the top of each curve; the catalysed value is the smaller» ✔
(ii) increase the pressure
OR
increase the concentration of the reactants ✔
Schemat punktowania
(i) [3]: M1 two curves with a maximum and a common finishing point, M2 ΔH labelled, M3 both activation energies labelled. Award [1] maximum for one curve drawn and correctly labelled. Accept double-headed arrows, and Ecat for the catalysed activation energy. Do not penalize a curve with several steps for the catalysed pathway. ECF from 2c(i). (ii) [1]: accept increasing the surface area of the solid catalyst; do not accept increasing the amount of reactant.