Energetics and Thermodynamics | AQA A-Level Chemistry (7405)
Energetics and Thermodynamics
- 108 questions
- 8 subtopics
- Physical chemistry, drawn on by Paper 1 and Paper 2
- Paper 1, Paper 2 and Paper 3
Energetics and thermodynamics is examined on Papers 1, 2 and 3, with thermodynamics on Paper 1 only.
It starts with measuring enthalpy change by calorimetry and Hess's law, then builds to Born-Haber cycles, entropy, and the free energy calculation that decides whether a reaction happens at all.
Sample questions from Energetics and Thermodynamics
Answer each one closed book first, then open the answer.
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Enthalpy Change and Standard Conditions
What does the term exothermic mean in relation to a reaction?
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A reaction that releases heat energy to the surroundings (negative ΔH) -
Calorimetry and Heat Change Calculations
How would you calculate the molar enthalpy change from the heat change measured in a calorimetry experiment?
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Divide the heat change (q) by the number of moles of the limiting reactant -
Hess's Law and Enthalpy Cycles
When using enthalpies of formation to calculate the enthalpy change of a reaction, what is the general formula?
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ΔH = Σ ΔfH(products) − Σ ΔfH(reactants) -
Mean Bond Enthalpies
In a reaction, what happens to bonds in the reactants and what happens to form products?
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Bonds in reactants are broken and new bonds are formed in products. -
Lattice Enthalpy and Born-Haber Cycles
What is enthalpy of atomisation?
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The enthalpy change when one mole of gaseous atoms is formed from an element in its standard state under standard conditions -
Enthalpies of Solution and Hydration
What three enthalpy terms are related in the enthalpy cycle for dissolving an ionic compound?
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Lattice enthalpy, enthalpies of hydration of the cation and anion, and enthalpy of solution. -
Entropy Change
What happens to entropy when the number of moles of gas increases in a reaction?
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Entropy increases -
Gibbs Free Energy and Reaction Feasibility
For an endothermic reaction with a positive entropy change, how does increasing temperature affect the feasibility of the reaction?
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Increasing temperature makes the reaction more feasible because the negative contribution from –TΔS becomes larger, making ΔG more negative
The 8 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Enthalpy Change and Standard Conditions | Exothermic and endothermic changes, standard conditions, and the standard enthalpy definitions. | 15 |
| Calorimetry and Heat Change Calculations | Using q = mcΔT, converting to enthalpy change per mole, and the sources of error. | 16 |
| Hess's Law and Enthalpy Cycles | Hess's law, and building cycles from enthalpies of formation or combustion. | 12 |
| Mean Bond Enthalpies | Why bond enthalpies are averages, and estimating enthalpy change from bonds broken and made. | 10 |
| Lattice Enthalpy and Born-Haber Cycles | The enthalpy definitions a Born-Haber cycle needs, and constructing the cycle to find lattice enthalpy. | 13 |
| Enthalpies of Solution and Hydration | Enthalpy of solution and of hydration, and linking them through the lattice enthalpy. | 15 |
| Entropy Change | Entropy as a measure of disorder, predicting its sign, and calculating ΔS for a reaction. | 12 |
| Gibbs Free Energy and Reaction Feasibility | ΔG = ΔH − TΔS, the condition for feasibility, and finding the temperature at which it is met. | 15 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
AQA A-Level Chemistry Active Recall Guide
Every topic, not just this one. 2,442 questions with their answers.