Class 12 Chemistry Thermodynamics Notes and Important Questions
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Notes for Class 12 Thermodynamics (Chemistry) are shown above.
Practice
Important Questions
Define standard heat of formation. Calculate the heat of formation of acetic acid from the following data:
C(s) + O₂(g) → CO₂(g), ΔH = −99 kcal/mol
H₂(g) + 1/2 O₂(g) → H₂O(l), ΔH = −68 kcal/mol
CH₃COOH(l) + 2O₂(g) → 2CO₂(g) + 2H₂O(l), ΔH = −208 kcal/mol
Gibb’s free energy was introduced to explain spontaneity of thermodynamic process. Mathematically, ΔG = ΔH – TΔS
Define Gibb’s free energy change.
Predict the spontaneity if ΔH and ΔS are positive.
ΔH and ΔS for chemical reaction is found to be 50 kJ mol⁻¹ and 300 J mol⁻¹ K⁻¹. Is the reaction spontaneous at 15°C?
Gibbs-Helmholtz equation is represented as . For what value of will the reaction be spontaneous?
Positive
Zero
Negative
Infinite
What is the bond energy of C–H bond of CH₄ for the given reaction?
C + 4H → CH₄, ΔH = –400 kcal
100 kcal
–100 kcal
200 kcal
–400 kcal
Define heat of formation. Calculate the heat of formation of ethyl alcohol from given data.
Compound/Element — Heat of Combustion
Carbon → –94 Kcal
Hydrogen → –68.5 Kcal
Ethyl alcohol → –330 Kcal
Study the following data for the thermodynamic process H₂O(l) ⟶ H₂O(s) at different temperatures and at 1 atmospheric pressure.
Condition | Temperature | Entropy of system (J K⁻¹ mol⁻¹) | Entropy of surrounding |
|---|---|---|---|
1 | −1°C | −25.68 | +25.72 |
2 | 0°C | −26.55 | +26.88 |
3 | +1°C | −27.62 | +27.42 |
Calculate the total entropy of the universe at given condition 3.
Can we predict the spontaneity of the given reaction at 0°C?
Calculate the equilibrium constant for the fusion of ice at 1°C. What is the effect of temperature for the entropy change of reaction?
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Past Question Analysis
Historical exam-pattern data from past NEB question papers — not a prediction of future questions.
2
Question Items
0
Total Marks
1
Papers Appeared In
| Year | Question Items | Marks |
|---|---|---|
| 2082 | 2 | — |
Also appears in 5 model questions (not counted above — model sets aren't actual NEB exam history).
Thermodynamics deals with energy changes associated with chemical reactions and physical processes. Students study internal energy, the First and Second Laws of Thermodynamics, enthalpy, entropy, Hess's law, thermochemical changes and Gibbs free energy to determine the spontaneity of reactions.
This page covers Thermodynamics, chapter 5 of 22 in the Class 12 Chemistry syllabus set by the National Examination Board (NEB). 7 important questions for this chapter are available, each with a full solution.
For numerical and derivation-based chapters like this one, working through past NEB questions is usually more useful than re-reading notes alone — try solving each important question above before checking the solution, then compare your working step by step.