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Thermochemical Equations and Hess’s Law Class 11 MCQs – Free Online Practice Test
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Introduction
Mastering Thermochemical Equations and Hess’s Law is an essential part of CBSE Class 11 Chemistry. This online MCQ practice test is designed to strengthen your understanding of Thermodynamics (Chapter 6, Part A – Physical Chemistry). Each question is based on the latest NCERT syllabus, helping you prepare effectively for your school exams and competitive entrance tests like JEE and NEET.
In this quiz, students will explore how enthalpy, internal energy, and heat changes are related in chemical reactions. The questions emphasize the application of Hess’s Law, which allows calculating enthalpy changes for reactions that cannot be measured directly in laboratories.
This interactive quiz includes 30 multiple-choice questions with instant scoring and feedback to help you evaluate your performance in real-time. Practice these MCQs to build a strong foundation in thermochemistry and boost your exam confidence.
Highlight: These MCQs are strictly NCERT-based and are perfect for CBSE Class 11 students aiming for board exam excellence.
Sample MCQs (with Answers and Explanations)
Q1. The enthalpy change for a reaction at constant pressure is known as:
A) Internal energy change
B) Work done
C) Enthalpy change (ΔH)
D) Gibbs free energy
Answer: C) Enthalpy change (ΔH)
Explanation: At constant pressure, the heat absorbed or released equals the enthalpy change of the reaction (ΔH = qₚ).
Q2. Hess’s Law is valid because:
A) Heat is a path function
B) Enthalpy is a state function
C) Work done depends on the path
D) Enthalpy changes with rate
Answer: B) Enthalpy is a state function
Explanation: Since enthalpy depends only on initial and final states, the total enthalpy change remains constant, validating Hess’s Law.
Q3. For the reaction C(graphite) + O₂ → CO₂, ΔH = –393.5 kJ/mol. This represents:
A) Enthalpy of combustion
B) Enthalpy of formation
C) Bond enthalpy
D) Lattice enthalpy
Answer: B) Enthalpy of formation
Explanation: Formation enthalpy is the energy change when one mole of a compound forms from its elements in their standard states.
Q4. When a reaction is reversed, the enthalpy change becomes:
A) Same
B) Doubled
C) Negated
D) Zero
Answer: C) Negated
Explanation: Reversing a chemical reaction changes the sign of ΔH but not its magnitude.
Q5. If ΔH₁ = +50 kJ for A → B and ΔH₂ = –80 kJ for B → C, then ΔH for A → C equals:
A) +130 kJ
B) –30 kJ
C) +30 kJ
D) –130 kJ
Answer: B) –30 kJ
Explanation: Using Hess’s Law, ΔH(A→C) = ΔH₁ + ΔH₂ = +50 + (–80) = –30 kJ.