Zadanie 1b
Wzorowane na: Chemistry HL Paper 2, May 2026, TZ1, pytanie 1(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 1a-1f.
Nitric acid, HNO3, is manufactured industrially from ammonia in a three-step process known as the Ostwald process.
Polecenie
The second step converts nitrogen monoxide to nitrogen dioxide.
2 NO(g) + O2(g) ⇌ 2 NO2(g) ΔH⊖ = −114 kJ mol−1
(i) Identify the oxidation state of nitrogen in NO and in NO2.
(ii) State the equilibrium constant expression, Kc, for this reaction.
(iii) State, with a reason, the effect of increasing the temperature on the value of the equilibrium constant, Kc.
(iv) Discuss the effect of decreasing the volume of the system on the position of equilibrium and on the value of Kc.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
(i) NO: +2 AND NO2: +4 ✔
(ii) ✔
(iii) Kc decreases AND the forward reaction is exothermic «ΔH⊖ is negative, so the position moves towards the reactants» ✔
(iv) M1: the position of equilibrium shifts to the right/towards the products AND there are fewer moles of gas on the product side «2 mol against 3 mol» ✔
M2: Kc stays the same «it changes only with temperature» ✔
Schemat punktowania
(i) [1] both oxidation states correct; accept II and IV; do not accept 2+/2 or 4+/4. (ii) [1] correct expression with square brackets, products over reactants and the powers 2, 2 and 1; accept K in place of Kc. (iii) [1] one marking point: decreases AND the forward reaction is exothermic (OWTTE). (iv) [2] M1: shifts right/towards products AND fewer moles of gas; accept "shifts right AND to reduce the pressure"; M2: Kc unchanged; the reason for M2 is not required. Allow [1 max] if both directions are correct (right, unchanged) without correct explanations.