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Worksheets3.1.8.2 Free energy change + entropy change (A-level only)
Total questions: 10
Worksheet time: 5mins
A reaction is exothermic and has a negative entropy change.
Which statement is correct?
The reaction is always feasible
The reaction is feasible above a certain temperature
The reaction is feasible below a certain temperature
The reaction is never feasible
Which one of the equations below represents a reaction that is feasible at all temperatures?
P(s) → Q(s) + R(g) endothermic
2L(g) + M(g) → 2N(g) exothermic
S(g) → 2T(g) exothermic
A(g) + B(g) → C(g) endothermic
Which one of the following reactions in aqueous solution has the most positive change in entropy?
[Cu(H2O)6]2+ + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 4H2O
[Cu(H2O)6]2+ + 4Cl− → [CuCl4]2− + 6H2O
[Cu(H2O)6]2+ + EDTA4− → [Cu(EDTA)]2− + 6H2O
[Cu(H2O)6]2+ + 2H2NCH2CH2NH2 → [Cu(H2NCH2CH2NH2)2(H2O)2]2+ + 4H2O
Refer to the reaction in the image
Which one of the following statements is correct?
This is a redox reaction.
The reaction is not feasible below 298 K
At equilibrium, the yield of hydrogen iodide is changed by increasing the pressure.
At equilibrium, the yield of hydrogen iodide increases as the temperature is increased.
This question is about the reaction given below.
CO(g) + H2O(g) ⇌ CO2(g) + H2(g)
Enthalpy data for the reacting species are given in the table
Which one of the following statements is not correct?
The value of Kp changes when the temperature changes.
The activation energy decreases when the temperature is increased.
The entropy change is more positive when the water is liquid rather than gaseous.
The enthalpy change is more positive when the water is liquid rather than gaseous.
Using the information below, answer this question.
Fe2O3(s) + 3H2(g) → 2Fe(s) + 3H2O(g)
ΔH= +96 kJ mol−1, ΔS = +138 J K−1 mol−1
The standard entropy value for steam is
+332 J K−1 mol−1
+189 J K−1 mol−1
+145 J K−1 mol−1
+85 J K−1 mol−1
In which one of the following reactions is there a decrease in entropy?
[Fe(H2O)6]3+(aq) + 3C2O42- (aq) → [Fe(C2O4)3]3−(aq) + 6H2O(l)
[Cu(H2O)6]2+(aq) + EDTA4−(aq) → [Cu(EDTA)]2−(aq) + 6H2O(l)
[CoCl4]2−(aq) + 6H2O(l) → [Co(H2O)6]2+(aq) + 4Cl− (aq)
Na2CO3(s) + 2H+(aq) → 2Na+(aq) + CO2(g) + H2O(l)
This question relates to the equilibrium gas-phase synthesis of sulphur trioxide:
2SO2(g) + O2(g) ⇌ 2SO3(g)
Thermodynamic data for the components of this equilibrium are given in the table.
This equilibrium, at a temperature of 585 K and a total pressure of 540 kPa, occurs in a vessel of volume 1.80 dm3. At equilibrium, the vessel contains 0.0500 mol of SO2(g), 0.0800 mol of O2(g) and 0.0700 mol of SO3(g).
The standard entropy change for this reaction is
−222 J K−1 mol−1
−195 J K−1 mol−1
−186 J K−1 mol−1
+198 J K−1 mol−1
The following information concerns the equilibrium gas-phase synthesis of methanol.
CO(g) + 2H2(g) ⇌ CH3OH(g)
At equilibrium, when the temperature is 68 °C, the total pressure is 1.70 MPa.
The number of moles of CO, H2 and CH3OH present are 0.160, 0.320 and 0.180, respectively.
Thermodynamic data are given.
The standard entropy change for this reaction is
−220 J K−1 mol−1
+220 J K−1 mol−1
−89 J K−1 mol−1
+89 J K−1 mol−1
The compound lithium tetrahydridoaluminate(III), LiAlH4, is a useful reducing agent. It behaves in a similar fashion to NaBH4. Carbonyl compounds and carboxylic acids are reduced to alcohols. However, LiAlH4 also reduces water in a violent reaction so that it must be used in an organic solvent.
Which one of the following concerning the violent reaction between LiAlH4 and water is false?
A gas is produced.
The activation energy for the reaction is relatively high.
The reaction has a negative free-energy change.
Aqueous lithium ions are formed.
