Wzorowane na: Chemistry HL Paper 2, specimen 2025, pytanie 5(f). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Informacja do zadań 5a-5g.
Pentadecane,
Butan-2-ol reacts with octadecanoic (stearic) acid to form an ester that is used as a lubricant.
(i) Identify the by-product X(l) and state the type of reaction taking place.
(ii) Calculate the atom economy for the formation of the ester.
(iii) Discuss why manufacturers take the atom economy into account when assessing the impact of an industrial reaction.
(iv) Treating the system as homogeneous, deduce the expression for the equilibrium constant, , of this reaction.
(i) condensation / esterification AND / water ✔
(ii) «(ester) = 22(12.01) + 44(1.01) + 2(16.00) = 340.66; (H2O) = 18.02»
atom economy = « × 100 =» 95.0 % ✔
(iii) Any two of:
a high atom economy means that most of the atoms in the reactants end up in the useful product, so raw materials are used efficiently ✔
less waste / by-product is formed, which lowers disposal costs and environmental impact ✔
the process is more economical ✔
the process is more sustainable / conserves resources ✔
(iv)
(i) [1]: both the reaction type and water required. (ii) [1]: 95.0 % (accept 94.9–95.0 %). (iii) [2 max]. (iv) [1]: accept [X] in place of [H2O]; all four concentrations required, water must not be omitted.
The ester is the desired product, so its molar mass goes in the numerator; the atom economy is high because the only by-product is water.
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