Zadanie 4a
Wzorowane na: Chemistry HL Paper 2, May 2022, TZ2, pytanie 4(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 4a-4d.
Nitrogen dioxide is a brown gas formed in vehicle engines. Its reactions illustrate how rates and equilibria are studied.
Polecenie
The reaction between nitrogen dioxide and carbon monoxide was studied at 600 K.
NO2(g) + CO(g) → NO(g) + CO2(g)
The following experimental data were obtained.
| Experiment | Initial concentration of NO2 / mol dm−3 | Initial concentration of CO / mol dm−3 | Initial rate / mol dm−3 s−1 |
|---|---|---|---|
| 1 | 4.0 × 10−3 | 5.0 × 10−3 | 4.8 × 10−6 |
| 2 | 8.0 × 10−3 | 5.0 × 10−3 | 1.92 × 10−5 |
| 3 | 8.0 × 10−3 | 1.00 × 10−2 | 1.92 × 10−5 |
(i) Deduce the order of reaction with respect to nitrogen dioxide.
(ii) Deduce the rate expression for the reaction.
(iii) Calculate the value of the rate constant, stating its units.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) second order ✔ «doubling [NO2] at constant [CO] (experiments 1 and 2) makes the rate four times greater»
(ii) rate = k[NO2]2 ✔ «experiments 2 and 3: doubling [CO] has no effect, so zero order in CO»
(iii) «» 0.30 ✔
mol−1 dm3 s−1 ✔
Schemat punktowania
(i) [1]. (ii) [1]; the rate expression must not contain [CO]. (iii) M1: value of k from any experiment (0.30); M2: correct units. Award M2 for units consistent with the student's rate expression.