Thermodynamics (A Level only) (AQA A Level Chemistry)

Exam Questions

4 hours31 questions
11 mark

Which of the following represents the second ionisation energy of strontium? 

  • Sr+ (s) → Sr2+ (aq) + e-

  • Sr (s) → Sr2+ (g) + 2e-

  • Sr+ (g) → Sr2+ (g) + e-

  • Sr (g) → Sr2+ (g) + 2e-

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21 mark

Ammonia is produced according to the following gas-phase synthesis:

                                                  N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

Thermodynamic data for the components of this equilibrium are:

Substance 

  N2 (g)

    H2 (g)

    NH3 (g) 

SӨ (J K-1 mol-1)

  191.5

   130.6

    192.5

The standard entropy change for this reaction is

  • -129.6 J K-1 mol-1

  • -198.3 J K-1 mol-1

  • 198.3 J K-1 mol-1

  • 514.6 J K-1 mol-1

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31 mark

Which of the following is the correct equation for Gibbs free energy?

  • ΔG = ΔH - TΔS

  • ΔG = ΔH + TΔS

  • ΔG = TΔS - ΔH

  • ΔG = ΔS + TΔH

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41 mark

The reaction between graphite and oxygen is as follows

                                   C (s) + O2 (g) → CO2 (g)           ΔHf = -394 kJ mol-1

The entropy change for this reaction is (+)3 J K-1 mol-1. The free energy change for this reaction at 298 K is

  • -395 kJ mol-1

  • -1288 kJ mol-1

  • -500 kJ mol-1

  • 393 kJ mol-1

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51 mark

Which of the following best explains why lithium oxide has a much larger lattice enthalpy than potassium oxide?

  • Lithium ions have a greater charge than potassium ions

  • Potassium oxide has a greater Mr than lithium oxide

  • Potassium ions have a greater charge than lithium ions

  • Lithium ions have a smaller ionic radius than potassium ions

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61 mark

Which of the following represents the first electron affinity of oxygen?

  • O (g) + e- → O- (g)

  • 2O (g) + 2e- → 2O- (g)

  • O (g) + 2e- → O2- (g)

  • O- (g) → O (g) + e-

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11 mark

Ethene is produced according to the following gas-phase synthesis:

                                                 2C (s)  + 2H2 (g) → C2H4 (g) 

Thermodynamic data for the components of this equilibrium are

Substance             

  C (s)    

   H2 (g)    

   C2H4 (g)

ΔHϴf (kJ mol-1

    0

      0

       52

Sϴ (J K-1 mol-1)

    6

    131

      219

The free energy change for this reaction at 330 K is:

  • + 18202 kJ mol-1

  • + 33.83 kJ mol-1

  • + 70.15 kJ mol-1

  • -18098 kJ mol-1

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21 mark

Which of the following conditions will mean a reaction is never feasible?

 

    ΔH      

     ΔS  

  Temperature

A

   Negative 

    Positive 

 High

  B  

Positive

    Negative

 High

C

 Negative

      Negative 

 Low

D

 Positive 

    Positive

   High

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    31 mark

    Which of the following will show the least covalent character?

    • Beryllium bromide

    • Aluminium bromide

    • Potassium bromide

    • Magnesium bromide

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    41 mark

    Thermodynamic data for the components for magnesium oxide are 

    Name of enthalpy change

    Energy change (kJ mol-1)

    Enthalpy of formation of magnesium oxide

    -602

    Enthalpy of atomisation of magnesium 

    +150

    First ionisation energy of magnesium  

    +738

    Second ionisation energy of magnesium  

    +1450

    Enthalpy of atomisation of oxygen

    +248

    First electron affinity of oxygen

    -142

    Second electron affinity of oxygen

    +844

    The lattice enthalpy of formation for magnesium oxide is:

    • -4174 kJ mol-1

    • -3890 kJ mol-1

    • -3766 kJ mol-1

    • -4138 kJ mol-1

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    51 mark

    Using the information in the table to answer the question 

      Ion

          Value (kJ mol-1)

         ΔHӨlatt CaF2

    (+)2651

           ΔHӨhyd Ca2+ 

    -1616

         ΔHӨhyd F- 

    -504

    Which of the following is the correct value for the enthalpy change of solution, ΔHӨsol, of calcium fluoride, CaF2

    • +531 kJ mol-1

    • +5275 kJ mol-1

    • +27 kJ mol-1

    • -1589 kJ mol-1

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    11 mark

    Which compound would have the greatest difference between the theoretical and experimental value for lattice enthalpy?

    • AgCl

    • AgI

    • NaF

    • NaCl

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    21 mark

    Which row correctly describes a reaction that  is only feasible at a low temperature?

    • X (g) + Y (g) → Z (g)          exothermic

    • R (s) → T (g) + U (g)          endothermic

    • E (g) → 3F(g)          endothermic

    • M (g) + 2N (g) → P (g) + Q (g)          endothermic

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    31 mark

    Use the data in the table to calculate the value of the first electron affinity of iodine

    Name of enthalpy change

    Energy change (kJ mol-1)

    Enthalpy of atomisation of calcium 

    +178

    1st ionisation energy of calcium

    +590

    2nd ionisation energy of calcium 

    +1145

    Enthalpy of atomisation of iodine

    +107

    Lattice energy of calcium iodide 

    -2074

    Enthalpy of formation of calcium iodide 

    -534

    • -294 kJ mol-1

    • -240 kJ mol-1

    • -480 kJ mol-1

    • -587 kJ mol-1

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    41 mark

    Urea reacts with water to produce carbon dioxide and ammonia via the following reaction

    CO(NH2)2 (aq) + H2O (l) → CO2 (g) + 2NH3 (g)              ΔH = 133 kJ mol-1

    Thermodynamic data for the components of this reaction are

           Substance 

      CO(NH2)2 (aq)

       H2O (l)

        CO2 (g)

        NH3 (g)

         S (J K-1 mol-1

                105

           70

         214

         192

    At which of the following temperatures will this reaction become feasible?

    • 0.31 K

    • 3.18 K

    • 132.6 K

    • 314 K

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    51 mark

    Which of the following statements correctly explains the trend in enthalpy of hydration of the metal ions down Group 1?

    • The attraction between the ion and the hydrogen ions in water decreases down the group

    • The attraction the ion and the delta positive hydrogen atoms in water decreases down the group

    • The lone pair on the oxygen atom becomes more available for bonding

    • The attraction between the ion and the delta negative oxygen atoms in water decreases down the group

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