Zadanie 2f
Wzorowane na: Chemistry HL Paper 2, November 2023, TZ1, 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.
Hydrogen iodide forms from its elements in the gas phase according to the equilibrium
H2(g) + I2(g) ⇌ 2 HI(g)
Polecenie
The reaction is usually carried out at a high temperature in the presence of a catalyst.
(i) On the axes provided, sketch the energy profile of the reaction for the uncatalysed and for the catalysed pathway, and show ΔH and the activation energies.
(ii) State one way, apart from raising the temperature or adding a catalyst, of increasing the rate of the reaction.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) two profiles, each rising to a single peak AND starting at the level of H2 + I2 and ending at the same lower level of 2 HI ✔
exothermic enthalpy change labelled: ΔH is the difference in level between reactants and products, with products slightly lower ✔
both activation energies correctly labelled: Ea from the reactants to the top of the uncatalysed curve, and Ecat from the reactants to the top of the lower catalysed curve ✔
(ii) increase the pressure ✔
OR
increase the concentration of H2 or I2 ✔
Schemat punktowania
(i) M1: two curves with a maximum, same start and finish; M2: ΔH labelled, with products below reactants; M3: both activation energies labelled. A multi-step catalysed path is not penalized in M1. Double-headed arrows or plain lines are acceptable for marking ΔH and Ea in M2 and M3, and Ecat may label the catalysed activation energy. If only one profile is drawn and labelled correctly, the maximum is [1]. (ii) [1]. Accept increase in concentration of a reactant, but not an increase in the amount of a reactant.