What is the enthalpy change when 2 moles of water vapor condense to liquid water

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Question: What is the enthalpy change when 2 moles of water vapor condense to liquid water at constant temperature?

Options:

Correct Answer: -2ΔH_vap

Solution:

The enthalpy change is -2ΔH_vap, as condensation releases heat equal to twice the enthalpy of vaporization.

What is the enthalpy change when 2 moles of water vapor condense to liquid water at constant temperature?

What is the enthalpy change when 2 moles of water vapor condense to liquid water at constant temperature?

Step 1: Understand that enthalpy change (ΔH) is the heat energy change during a process.
Step 2: Know that when water vapor condenses to liquid water, it releases heat.
Step 3: Identify that the enthalpy of vaporization (ΔH_vap) is the amount of heat needed to turn liquid water into vapor.
Step 4: Realize that during condensation, the same amount of heat is released, but as a negative value because heat is leaving the system.
Step 5: Since we are condensing 2 moles of water vapor, the total enthalpy change will be -2 times the enthalpy of vaporization.
Step 6: Write the final expression for the enthalpy change as -2ΔH_vap.

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