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NCERT-Based Class 11 Chemistry Quiz on Gibbs Energy and Spontaneity
Introduction
Understanding Spontaneity and Gibbs Energy is essential in CBSE Class 11 Chemistry, especially under the chapter Thermodynamics. This concept helps students predict whether a reaction will occur on its own under specific conditions. To strengthen your grasp, this online MCQ practice test includes multiple-choice questions aligned strictly with the NCERT Class 11 Chemistry syllabus.
These MCQs test your understanding of enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) relationships that govern spontaneity and equilibrium. Each question comes with detailed explanations to help you identify and correct conceptual gaps.
Designed for CBSE Class 11 board exam preparation, these quizzes are equally useful for JEE and NEET aspirants aiming to build a solid foundation in physical chemistry. Attempt all 30 questions within a 30-minute timer and get instant scoring and feedback.
Start practicing now and boost your confidence in the topic “Spontaneity and Gibbs Energy” — a key part of thermodynamics in Class 11 Chemistry.
Sample MCQs (With Answers and Explanations)
Q1. Which condition must be satisfied for a process to be spontaneous at constant temperature and pressure?
A) ΔH > 0, ΔS > 0
B) ΔH < 0, ΔS > 0
C) ΔH < 0, ΔS < 0
D) ΔH > 0, ΔS < 0
✅ Answer: B) ΔH < 0, ΔS > 0
Explanation: A process is spontaneous when Gibbs free energy change (ΔG = ΔH – TΔS) is negative. When ΔH is negative and ΔS positive, ΔG < 0 at all temperatures.
Q2. For a reaction with ΔH = 60 kJ mol⁻¹ and ΔS = 200 J K⁻¹ mol⁻¹, at what temperature will it become spontaneous?
A) Above 300 K
B) Below 300 K
C) At 273 K
D) Never spontaneous
✅ Answer: A) Above 300 K
Explanation: ΔG = ΔH – TΔS. The reaction becomes spontaneous when ΔG < 0 → T > ΔH/ΔS = 60000/200 = 300 K.
Q3. At equilibrium, the value of ΔG for a reaction is:
A) Negative
B) Positive
C) Zero
D) Undefined
✅ Answer: C) Zero
Explanation: At equilibrium, the system has no net driving force in either direction; therefore, ΔG = 0 for reversible processes at constant T and P.
Q4. Which relation correctly connects Gibbs free energy and equilibrium constant (K)?
A) ΔG° = RT ln K
B) ΔG° = -RT ln K
C) ΔG° = -K
D) ΔG° = TΔS
✅ Answer: B) ΔG° = -RT ln K
Explanation: The relation between Gibbs energy and equilibrium constant is ΔG° = -RT ln K, where R is the gas constant and T is temperature in kelvin.
Q5. What does a positive value of ΔG indicate about a reaction?
A) Spontaneous
B) Non-spontaneous
C) At equilibrium
D) Irreversible
✅ Answer: B) Non-spontaneous
Explanation: A positive ΔG means the reaction is not spontaneous under the given conditions and requires external energy input.
✅ Perfect for:
Students preparing for CBSE Class 11 board exams, JEE Main, or NEET Chemistry.