JEE Main Chemistry: Enthalpy of reaction, fusion and vaporization, and lattice enthalpy Practice Questions
14 free multiple-choice questions on Enthalpy of reaction, fusion and vaporization, and lattice enthalpy (Chemical Thermodynamics) for JEE Main Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more JEE Main questions in the app →Q1. The energy required to convert a solid directly into a liquid at its melting point is known as:
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Correct answer: D — Enthalpy of fusion
The enthalpy of fusion (ΔH₍fus)) or enthalpy of fusion is the heat absorbed during the phase transition from solid to liquid.
Q2. Which thermodynamic quantity is directly related to the amount of heat absorbed or released when a system undergoes a chemical reaction at constant pressure?
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Correct answer: B — Enthalpy of reaction
The enthalpy of reaction (ΔHᵣₓₙ) is the heat absorbed or released during a chemical reaction at constant pressure, directly related to the First Law of Thermodynamics.
Q3. Which term refers to the energy change associated with the formation of a new ionic solid from its constituent gaseous ions?
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Correct answer: B — Lattice enthalpy
Lattice enthalpy is specifically the energy change released when gaseous ions combine to form one mole of a solid crystal lattice.
Q4. Which of the following processes generally involves the absorption of energy from the surroundings?
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Correct answer: C — Endothermic reaction
An endothermic process is one that absorbs heat from its surroundings, requiring an input of energy.
Q5. Which statement correctly describes the relationship between enthalpy of fusion and enthalpy of vaporization for a pure substance?
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Correct answer: A — ΔH₍fusion) is always less than ΔH₍vaporization)
For most substances, the energy required to melt (fusion) is less than the energy required to vaporize (vaporization).
Q6. The latent heat of vaporization is the energy absorbed during the process of:
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Correct answer: D — Vaporizing a liquid
Latent heat of vaporization is the energy absorbed by the substance to change its state from liquid to gas (vaporization).
Q7. Lattice enthalpy of an ionic solid primarily reflects the stability gained by forming the crystal structure. This energy is primarily associated with which interaction?
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Correct answer: D — Electrostatic attraction between ions
Lattice enthalpy arises from the strong electrostatic forces of attraction between the oppositely charged ions held in the crystal lattice.
Q8. Which of the following statements is true regarding the enthalpy change (ΔH) of a spontaneous process?
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Correct answer: D — ΔH can be positive, negative, or zero.
A spontaneous process is characterized by a negative change in enthalpy (ΔH < 0). However, the question asks about the enthalpy change itself; it can be positive (endothermic) or negative (exothermic). Spontaneity is determined by ΔG, not solely ΔH.
Q9. Which of the following statements is a state function?
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Correct answer: C — Enthalpy
State functions are properties that depend only on the current state of the system (e.g., temperature, pressure, volume). Enthalpy is a classic state function.
Q10. Lattice enthalpy is primarily associated with the energy required to break the forces of attraction in which state of matter?
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Correct answer: B — Solid
Lattice enthalpy is the energy required to separate the ions from the crystal lattice, which relates directly to the stability of the solid crystal structure (solid state).
Q11. If a substance undergoes a process where heat is absorbed and the system moves to a higher energy state, the process is described as:
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Correct answer: A — Endothermic
A process that absorbs heat from the surroundings and results in an increase in the internal energy of the system is endothermic.
Q12. If a chemical reaction is highly exothermic, the overall enthalpy change (ΔH) for the process will be:
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Correct answer: B — Negative
An exothermic reaction releases heat energy to the surroundings, meaning the enthalpy change (ΔH) is negative.
Q13. When a substance changes from a solid to a liquid at its melting point, the process is characterized by:
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Correct answer: A — Phase change requiring latent heat
Melting is a phase change. The heat absorbed or released during a phase change at constant temperature is known as latent heat.
Q14. Which thermodynamic quantity represents the heat absorbed or released during a chemical reaction occurring at constant pressure?
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Correct answer: B — Enthalpy of Reaction
The enthalpy of reaction (ΔH) is defined as the heat absorbed or released in a chemical reaction at constant pressure.
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