Zadanie 2b
Wzorowane na: Chemistry HL Paper 2, May 2026, TZ3, pytanie 2(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 2a-2c.
Sulfur dioxide, SO2, is a covalently bonded compound and a common air pollutant released when sulfur-containing fuels burn.
Polecenie
The oxidation of sulfur dioxide to sulfur trioxide is an equilibrium reaction.
2 SO2(g) + O2(g) ⇌ 2 SO3(g)
(i) State the equilibrium constant expression, K, for the reaction.
(ii) Explain, with a reason, how compressing the gas mixture at constant temperature will affect the equilibrium position and the value of the equilibrium constant, K.
(iii) For a certain reaction, the value of the reaction quotient, Q, was found to be less than the value of the equilibrium constant, K. Explain the difference between Q and K and predict the direction of the spontaneous process for this reaction.
(iv) Explain why the rate of the reaction increases when the temperature of the mixture is raised from 700 K to 800 K.
(v) The Maxwell–Boltzmann energy distribution curve for the mixture at temperature T1 is shown below. Sketch a curve at a lower temperature and label it T2.
(vi) State the effect on the activation energy, Ea, of lowering the temperature from T1 to T2.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
(i) ✔
(ii) Equilibrium position: shifts to the right / towards the products AND fewer moles of gas on the right-hand side ✔
Value of K: unchanged AND K depends only on temperature ✔
(iii) K is calculated from concentrations at equilibrium AND Q from the same expression but with the concentrations at any other moment ✔
the reaction proceeds to the right / forward AND Q increases until it equals K
OR
the forward reaction is favoured AND reactants are used up and products formed until equilibrium is reached ✔
(iv) a greater proportion of molecules has energy ≥ Ea / the average kinetic energy is higher ✔
more frequent «successful» collisions per unit time
OR
a higher proportion of collisions is successful ✔
(v) curve for T2 starting at the origin AND asymptotic to the x-axis AND with its maximum higher than and to the left of the maximum of T1 ✔
(vi) no effect / unchanged ✔
Schemat punktowania
(i) [1]: square brackets; omit penalty for missing state symbols. (ii) [1] for the position with the reason (fewer gas moles on the right), [1] for K unchanged with the reason; award [1 max] for both effects without reasons. (iii) [1] for the difference between Q and K; [1] for the direction (right / forward) with its reason. (iv) [1] each. (v) [1]: the curve must start at the origin, not touch the axis again, and the peak must be higher and shifted left; the area under the two curves should look equal. (vi) [1].
Komentarz
In part (ii) the pressure is changed by changing the volume, so the position moves; adding an inert gas at constant volume would change nothing.