Zadanie 3a
Wzorowane na: Chemistry HL Paper 2, May 2022, TZ1, pytanie 3(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 3a-3c.
Methanol is produced industrially from carbon monoxide and hydrogen. The reaction involves the equilibrium:
CO(g) + 2 H2(g) ⇌ CH3OH(g)
The percentage of methanol in the equilibrium mixture, starting from carbon monoxide and hydrogen in a 1 : 2 mole ratio, under various conditions is shown:
Polecenie
(i) Deduce the expression for the equilibrium constant, Kc, for this equation.
(ii) State how the use of a catalyst affects the value of Kc.
(iii) Using the reaction quotient, Q, explain why raising the pressure at constant temperature increases the percentage of methanol at equilibrium.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) ✔
(ii) no effect / unchanged / the same ✔
(iii) increasing the pressure increases «all» concentrations
OR
increasing the pressure decreases the volume ✔
Q becomes less than Kc
OR
the denominator of Q «[CO][H2]2, three moles of gas» is affected more than the numerator «one mole of gas» ✔
«for Q to equal Kc again,» the mixture ends up with more product relative to reactants
OR
the equilibrium moves to the right / towards methanol ✔
Schemat punktowania
(i) [1]; square brackets must be used. (ii) [1]. (iii) M1: concentrations increase / volume decreases; M2: Q < Kc with a reason; M3: shift to the right restores Kc. An answer that never mentions Q earns at most [2].