Zadanie 2c
Wzorowane na: Chemistry SL Paper 2, May 2022, TZ1, pytanie 2(c). 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-2e.
Methanol, CH3OH, is an important industrial chemical used to make plastics, solvents and fuels. It is also the starting material for methylamine, CH3NH2, a gas used in the manufacture of pesticides and medicines.
Polecenie
Methanol is manufactured from carbon monoxide and hydrogen. The reaction involves the equilibrium:
CO(g) + 2 H2(g) ⇌ CH3OH(g)
(i) Deduce the expression for the equilibrium constant, Kc, for this equation.
(ii) Explain why an increase in pressure shifts the position of equilibrium towards the product, and state the effect of this change on the value of Kc.
(iii) State how the use of a catalyst affects the position of equilibrium.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) ✔
(ii) the equilibrium shifts towards the side with fewer moles of gas «1 mol of CH3OH against 3 mol of reactants», so the pressure is partly reduced / the volume of the gas mixture decreases ✔
Kc is unchanged «it depends only on temperature» ✔
(iii) no effect / unchanged / the same ✔
Schemat punktowania
(i) [1]; square brackets must be used. (ii) M1: shift to the right with a reason based on the numbers of moles of gas; M2: Kc unchanged. Accept “Kc is only changed by a change of temperature”. (iii) [1]; accept “it only makes equilibrium be reached sooner”.