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Zadanie 2e

5 pktotwarteśrednie (szac.)Paper 2, listopad 2022

Wzorowane na: Chemistry HL Paper 2, November 2022, pytanie 2(e). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.

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Informacja do zadań 2a-2e.

Compound P is a quinazoline derivative that has been investigated as an antimalarial drug candidate.

skeletal formula of compound P, a quinazoline derivative

Polecenie

Compound P can be synthesized by reacting 4,6-dichloroquinazoline with another reactant, B.

skeletal formulas of 4,6-dichloroquinazoline (left) and of compound P (right), the reaction being 4,6-dichloroquinazoline + B giving compound P

(i) Deduce the structure of B.

(ii) The reaction can be catalysed by copper(I) iodide, CuI. State the ground-state electron configuration of the Cu+ ion.

(iii) The graph shows the Maxwell–Boltzmann distribution of kinetic energies of the reacting particles at the temperature of the synthesis. Annotate the curve to show the activation energy, Ea, for the uncatalysed reaction and for the catalysed reaction.

Maxwell–Boltzmann distribution curve of the fraction of particles against kinetic energy, drawn without any activation energy marked

(iv) Explain, referring to the Maxwell–Boltzmann distribution curve, the effect of a catalyst on a chemical reaction.

Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja

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Odpowiedź z klucza

(i) primary amine / −NH2 group «at one end» ✔

rest of the structure: H2N−CH2CH2CH2−N(CH2CH3)2 «the 3-(diethylamino)propyl chain» ✔

(ii) 1s2 2s2 2p6 3s2 3p6 3d10 / [Ar]3d10 ✔

(iii) both Ea values marked on the kinetic energy axis AND the catalysed one labelled, lying to the left of the uncatalysed one ✔

(iv) increases the rate AND a greater proportion of particles / a greater area under the curve has kinetic energy ≥ Ea «for the catalysed reaction» ✔

Schemat punktowania

(i) M1: the amine group; M2: the rest of the structure. Accept condensed or skeletal formulas. Do not penalize the labelling of nitrogen. (ii) 1 mark; accept either order of the 3d and 4s sublevels, but the 4s sublevel must be empty. (iii) 1 mark, as in the key. (iv) 1 mark; do not award for general statements such as 'provides an alternative pathway' or 'lowers Ea' without reference to the distribution.

Komentarz

In (ii) copper(I) loses its single 4s electron; the 3d sublevel is full.

Umiejętności w zadaniu