Zadanie 4c
Wzorowane na: Chemistry HL Paper 2, May 2023, TZ1, pytanie 4(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 4b-4c.
A voltaic cell was constructed from an iron(II) sulfate/iron half-cell and a copper(II) sulfate/copper half-cell, connected by a salt bridge and, externally, by a wire.
Polecenie
(i) Calculate the standard cell potential for the voltaic cell. Use section 19 of the data booklet.
(ii) Calculate the standard Gibbs energy change, ΔG⊖, in kJ mol−1, for the cell reaction. Use sections 1 and 2 of the data booklet. (If you did not answer part (i), use 0.60 V, but this is not the correct value.)
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) «Ecell⊖ = Ecathode⊖ − Eanode⊖ = +0.34 − (−0.45) =» +0.79 V ✔
(ii) «ΔG⊖ = −nFEcell⊖ = −2 × 9.65 × 104 C mol−1 × 0.79 V» ✔
= −152.5 kJ mol−1 ✔
Alternative with the given 0.60 V: «−2 × 9.65 × 104 × 0.60 =» −115.8 kJ mol−1
Schemat punktowania
(i) [1]: accept ECF from 4b(ii). (ii) [2]: M1 for n = 2 with F and Ecell⊖; M2 for the value in kJ with a negative sign. Award [2] for the correct final answer; the answer to 3 significant figures (-152) is also accepted.