Work Done In Thermodynamics

Concept:
• Endothermic processes
• Exothermic processes

Step 1: Identify nature of each process.

• Ionisation Endothermic
• Sublimation Endothermic
• Vapourisation Endothermic
• Bond dissociation Endothermic
• Combustion Exothermic

Step 2: Select process with negative enthalpy.
Only combustion always releases heat.

Concept: Gibbs free energy: For spontaneity:

Step 1: Analyze condition.

• At low temperature reaction is spontaneous
• At high temperature reaction is non-spontaneous

Step 2: Apply equation.
If and :
• At low : (spontaneous)
• At high : (non-spontaneous)

Concept:

Step 1: Substitute.

Step 1: Understanding the Concept:
Enthalpy of reaction .

Step 2: Detailed Explanation:
for Fe(s) and H2(g) is 0 by definition.

.

Step 3: Final Answer:
The enthalpy of reaction is -33.29 kJ.

Step 1: Understanding the Concept:
Extensive properties depend on the amount of matter in the system (e.g., mass, volume). Intensive properties do not depend on the amount of matter (e.g., temperature, pressure, density).

Step 2: Detailed Explanation:
Analyze each property:
• (i) Volume: Depends on the amount of substance. Extensive.
• (ii) Pressure: Does not depend on the amount. Intensive.
• (iii) Density: Ratio of mass to volume. Does not depend on the amount. Intensive.
• (iv) Heat capacity: Amount of heat needed to raise temperature by 1K. Depends on the mass of the substance. Extensive.

Step 3: Final Answer:
The extensive properties are (i) Volume and (iv) Heat capacity.

Work done in expansion against constant external pressure is: Given: So, External pressure: Thus, Now use: So,
Hence, the correct answer is: