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Spontaneity Of Chemical Reactions — Syllabus

NIOS · Class 12 · Chemistry

What Spontaneity Of Chemical Reactions covers in NIOS Class 12 Chemistry: 4 topics, for the 2026-27 session. Part of the NIOS Class 12 Chemistry syllabus.

45 questions30 flashcards3 formulas & key relations5 concepts

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4 Topics · NIOS Class 12 Chemistry · 2026-27

Topics in Spontaneity Of Chemical Reactions

1

1. Spontaneous and Non-Spontaneous Processes

  • A spontaneous process occurs naturally without external intervention once initiated
  • Non-spontaneous processes require continuous external energy input to proceed
  • Examples of spontaneous processes: cooling of hot water, rusting of iron, mixing of gases, melting of ice below 0°C
2

2. Entropy and Disorder

  • Entropy (S) is a measure of disorder, randomness, or microstates in a system
  • Greater disorder in a system means higher entropy
  • Crystalline solids have the lowest entropy (most ordered)
3

3. The Second Law of Thermodynamics

  • The second law states: all spontaneous processes increase the entropy of the universe
  • For a spontaneous process: ΔS_universe = ΔS_system + ΔS_surroundings > 0
  • At equilibrium: ΔS_universe = 0 (no net change)
4

4. The Third Law of Thermodynamics

  • The third law states: the entropy of a pure, perfectly crystalline solid at absolute zero (0 K) is zero
  • This provides a reference point (entropy zero) from which all other entropy values are measured
  • Allows calculation of absolute entropy values for substances at any temperature above 0 K

Key Concepts

A spontaneous process is oneEntropy is a thermodynamic propertyThe second law states that allThe third law states thatFor a chemical reaction

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Frequently Asked Questions

What are the important topics in Spontaneity Of Chemical Reactions for NIOS Class 12 Chemistry?
Key topics in Spontaneity Of Chemical Reactions include Spontaneous and Non-Spontaneous Processes, Entropy and Disorder, The Second Law of Thermodynamics, The Third Law of Thermodynamics. Study these first, then practise questions on each for the NIOS Class 12 board exam.
How should I revise Spontaneity Of Chemical Reactions for the NIOS Class 12 board exam?
Learn the core ideas first, then work through the 45 practice questions on Spontaneity Of Chemical Reactions. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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