Zadanie 6a
Wzorowane na: Chemistry HL Paper 2, November 2024, pytanie 6(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
Nitrogen dioxide, NO2, is one of the brown pollutant gases in photochemical smog. It can react with carbon monoxide, which is also present in polluted air.
NO2(g) + CO(g) → NO(g) + CO2(g)
(i) Suggest how the rate of this reaction could be followed experimentally.
(ii) Determine the order of the reaction with respect to each reactant and write the rate expression.
| Experiment | [NO2] / mol dm−3 | [CO] / mol dm−3 | Initial rate / mol dm−3 s−1 |
|---|---|---|---|
| 1 | 0.010 | 0.020 | 5.0 × 10−5 |
| 2 | 0.010 | 0.040 | 5.0 × 10−5 |
| 3 | 0.020 | 0.040 | 2.0 × 10−4 |
(iii) Using the data from experiment 3, determine the value of the rate constant, k, and its units.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) measure the decrease in the intensity of the brown colour with time «for example with a colorimeter»
OR
analyse samples of the gas mixture taken at known times ✔
«pressure and volume cannot be used: the total amount of gas does not change, two moles of gas on each side»
(ii) CO: zero order AND NO2: second order ✔
rate = k[NO2]2 ✔
(iii) « =» 0.50 ✔
dm3 mol−1 s−1 ✔
Schemat punktowania
(i) [1]; do not accept a change without reference to time. Do not accept a change in pressure or volume, because the amount of gas is the same on both sides of the equation. (ii) M1: both orders; M2: rate expression. Award [2] for a correct rate expression. (iii) M1: value; M2: units.