Given below are two statements: Statement I: When a system containing ice in equilibrium with water (liquid) is heated,…
Chemical Equilibrium · Class 11 · JEE Main Previous Year Question
Given below are two statements:
Statement I: When a system containing ice in equilibrium with water (liquid) is heated, heat is absorbed by the system and there is no change in the temperature of the system until whole ice gets melted.
Statement II: At melting point of ice, there is absorption of heat in order to overcome intermolecular forces of attraction within the molecules of water in ice and kinetic energy of molecules is not increased at melting point.
In the light of the above statements, choose the correct answer from the options given below:
- a
Statement I is true but Statement II is false
- b
Both Statement I and Statement II are false
- c✓
Both Statement I and Statement II are true
- d
Statement I is false but Statement II is true
Both Statement I and Statement II are true
Step 1 — Analyse Statement I
At the melting point (0°C), ice and water coexist in equilibrium. When heat is supplied, it is used to break intermolecular hydrogen bonds in ice (latent heat of fusion = 6.01 kJ/mol). The temperature remains constant at 0°C until all ice melts.
Statement I is TRUE ✓
Step 2 — Analyse Statement II
At the melting point, the supplied heat (latent heat) overcomes the intermolecular forces of attraction (H-bonds) in ice. Since temperature is constant, kinetic energy of molecules does NOT increase — the energy goes into potential energy (breaking bonds), not kinetic energy.
Statement II is TRUE ✓
Step 3 — Answer: Both statements true → Option (c)
Key Points to Remember:
- Melting point = temperature at which solid and liquid are in equilibrium
- Latent heat of fusion: energy used to break intermolecular bonds, NOT to raise temperature
- Temperature remains constant during phase transition (constant KE)
- This is an example of physical equilibrium
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