Use ΔG° = -RT lnK to calculate K from standard Gibbs energy data or ΔG° from K, and interpret the result: a negative ΔG° means K greater than 1 and products favoured, a positive ΔG° means K less than 1 and reactants favoured.
Tę umiejętność sprawdza 16 zadań wzorowanych na arkuszach IB z lat 2022–2025.
Suppose carbonyl dibromide were made by a free-radical chain reaction of carbon monoxide, CO, with bromine vapour, Br2, started by ultraviolet light. The questions below treat this hypothetical route with the bond-enthalpy model and the entropy…
(i) An equilibrium mixture in a 25.0 dm3 reactor at 500 °C contains 15.0 mol N2, 22.5 mol H2 and 5.25 mol NH3. Calculate the equilibrium constant, K, for the reaction. (ii) The volume of the reactor containing the equilibrium…
(i) Calculate the enthalpy change, ΔH, for the overall synthesis of propyl ethanoate from propane and ethane shown above. Use section 12 of the data booklet. (ii) Two students each calculated the enthalpy change for the reaction between propan-1-ol and…
Carbon monoxide reacts with chlorine to form phosgene, COCl2. CO(g) + Cl2(g) ⇌ COCl2(g) K = 2.75 × 103 at 45 °C ΔG = −RTln K R = 8.31 J K−1 mol−1 What is the Gibbs energy change, ΔG, in…
At 1200 K, calculate ΔG⊖ for the forward reaction and the value of the equilibrium constant, K. Use sections 1 and 2 of the data booklet. If you were unable to obtain an answer for 3f, use 230 J K−1, but this is not the correct…
The equilibrium constant for the reaction below is Kc = 4.5 × 10−31 at 298 K. Which combination is correct? N2(g) + O2(g) ⇌ 2 NO(g) A. products are favoured and ΔG is positive B. products are favoured and ΔG is negative C.…
Which combination is correct for a reaction with an equilibrium constant K much smaller than 1 at 298 K under standard conditions? A. Ecell⊖ is negative and ΔG⊖ is positive B. Ecell⊖ is positive and…
Sulfuryl chloride, SO2Cl2, is made industrially from sulfur dioxide and chlorine in the presence of an activated carbon catalyst. SO2(g) + Cl2(g) ⇌ SO2Cl2(g) ΔH⊖ < 0 (i) Sketch a potential energy profile for the forward reaction,…
Which statements about the position of equilibrium are correct? ΔG⊖ = −RTln K I. If ΔG⊖ > 0, then K < 1 and the reactants are favoured. II. At equilibrium, ΔG⊖ is equal to zero. III. If ΔG⊖ = 0,…
Sulfur trioxide is manufactured industrially by the oxidation of sulfur dioxide. 2 SO2(g) + O2(g) ⇌ 2 SO3(g) ΔH⊖ = −198.0 kJ mol−1 (i) Outline what is meant by dynamic equilibrium. (ii) Deduce the Kc expression for this…
Four reactions at 298 K have the equilibrium constants listed below. Which constant belongs to the reaction with the lowest (most negative) standard Gibbs energy change, ΔG⊖? A. 2.7 × 103 B. 3.1 × 10−4 C. 9.5 × 10−2…
A reaction has a standard Gibbs energy change, ΔG⊖, of −8.0 kJ mol−1 at 298 K. Which statement about the equilibrium constant, K, and the equilibrium mixture is correct? A. K < 1; the equilibrium mixture contains mostly…
(i) Calculate the enthalpy change for this reaction, using section 13 of the data booklet and the values given below. (ii) Outline why the entropy change of this reaction is expected to be small. (iii) Ignore the entropy change. Use your answer to (i) together…
The standard free energy change, ΔG⊖, for the production of methanol is −44.0 kJ at 298 K and the standard enthalpy change, ΔH⊖, is −114 kJ. (i) State, with a reason, whether the production of methanol is spontaneous at 298 K.…
Consider the formation of gaseous nitrogen dioxide from liquid dinitrogen tetroxide. N2O4(l) → 2 NO2(g) ΔH⊖ = +85.9 kJ mol−1 (i) Calculate the entropy change of the reaction, ΔS⊖, in…
A student investigates the dissolution of ammonium chloride in water as the basis of an instant cold pack, in which solid ammonium chloride is kept apart from water by a thin membrane. The enthalpy change when one mole of solid ammonium chloride dissolves in…
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