Zadanie 4d
Propene can be reduced to propane by hydrogen gas in the presence of a platinum catalyst at 50 °C. Outline how the catalyst increases the rate of this reaction.
Catalysts and alternative reaction pathways
Explain how a catalyst provides an alternative pathway with lower activation energy, sketch energy profiles with and without a catalyst for exothermic and endothermic reactions, and show on a Maxwell-Boltzmann curve why more particles can react; enzymes are biological catalysts.
Tę umiejętność sprawdza 20 zadań wzorowanych na arkuszach IB z lat 2022–2026.
Zadania sprawdzające tę umiejętność: 20 Otwórz w wyszukiwarce z filtrami
Zadanie 29
The decomposition of hydrogen peroxide in the presence of iodide ions occurs in two steps. H2O2(aq) + I−(aq) → H2O(l) + IO−(aq) (slow) H2O2(aq) + IO−(aq) → H2O(l) + O2(g) + I−(aq) (fast) What is the role of I− in this mechanism? A.…
Zadanie 6a
In the first step, manganese(III) ions formed from the manganate(VII) are complexed by ethanedioate ions. [Mn(H2O)6]3+(aq) + 2 C2O42−(aq) → [Mn(C2O4)2(H2O)2]−(aq) + 4 H2O(l) (i) Deduce the oxidation state of carbon in [Mn(C2O4)2(H2O)2]−. (ii)…
Zadanie 3c
(i) Concentrated sulfuric acid, H2SO4, is used as the catalyst in the manufacture of propyl ethanoate. Explain how the catalyst affects the reaction. (ii) The conversion of propane into 1-bromopropane,…
Zadanie 3f
(i) Sketch the Maxwell–Boltzmann energy distribution curve for the particles in this reaction mixture at 25 °C, marking on the diagram the activation energy both with and without the catalyst. (ii) On the same axes, sketch and label a second Maxwell–Boltzmann…
- Materiał graficzny
Zadanie 3b
The forward reaction is endothermic, uses platinum as a catalyst, and takes place at 800 K. Sketch the reaction's energy profile both with and without the catalyst present, labelling the activation energies and ΔH.
- Materiał graficzny
Zadanie 27
Which of the following correctly describes the effect of a catalyst on a reaction? A. It increases the frequency of collisions between reactant particles B. It increases the proportion of collisions with energy greater than or equal to the activation energy C.…
Zadanie 3d
The Maxwell-Boltzmann distribution for the uncatalysed reaction at temperature T1 is shown below. Add annotations to show how a catalyst changes the situation.
- Materiał graficzny
Zadanie 3e
The reaction takes place on the surface of a nickel catalyst. The following mechanism is proposed, in which Ni-C represents carbon atoms bonded to the nickel surface: CH4 + Ni → Ni−C + 2 H2 (slow) Ni−C + CO2 → Ni−CO + CO (fast)…
- Materiał graficzny
Zadanie 6c
Iron(III) ions catalyse the decomposition of hydrogen peroxide but zinc ions do not. Outline why.
Zadanie 19
Potassium chlorate(V) was heated and the volume of oxygen collected was measured against time. The dotted line shows the result without a catalyst. The experiment is repeated at the same temperature with the same mass of potassium chlorate(V) and with…
- Materiał graficzny
Zadanie 2e
The oxidation of sulfur dioxide in industry requires a catalyst. (i) State how a catalyst increases the rate of this reaction. (ii) Sketch a Maxwell-Boltzmann distribution curve showing the activation energies with and without a catalyst. (iii) Suggest how the…
- Materiał graficzny
Zadanie 6b
Explain how a catalyst such as manganese(IV) oxide increases the rate of this reaction.
Zadanie 2f
The reaction is usually carried out at a high temperature in the presence of a catalyst. (i) On the axes provided, sketch the energy profile of the reaction for the uncatalysed and for the catalysed pathway, and show ΔH and the activation energies.…
- Materiał graficzny
Zadanie 2f
The conversion of carbon dioxide to methanol is usually carried out over a catalyst containing copper and zinc oxide. (i) Sketch energy profiles for the forward reaction, with and without the catalyst, on the axes shown. Label ΔH and the two activation…
- Materiał graficzny
Zadanie 19
Which statement correctly explains why a reaction is faster when a catalyst provides an alternative reaction pathway? A. It raises the average kinetic energy of the reacting particles. B. It lowers the activation energy, so a greater proportion of collisions…
Zadanie 19
How does a catalyst increase the rate of a reaction? A. It increases the average kinetic energy of the colliding particles. B. It lowers the activation energy so that a greater proportion of collisions are successful. C. It makes the reaction more exothermic.…
Zadanie 3a
(i) Deduce the expression for the equilibrium constant, Kc, for this equation. (ii) State how the use of a catalyst affects the value of Kc. (iii) Using the reaction quotient, Q, explain why raising the pressure at constant temperature increases the…
- Materiał graficzny
Zadanie 6a
Outline how the presence of the silver catalyst affects the rate of the reaction, and explain why.
Zadanie 2e
Compound P can be synthesized by reacting 4,6-dichloroquinazoline with another reactant, B. (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.…
- Materiał graficzny