Thermodynamics Terms

The reaction for the formation of water is as

;

On reversing E (i), we get

;


By heat water decomposed
heat will decompose water

For an irreversible expansion of an ideal gas under isothermal conditions, the temperature of the gas remains constant throughout the process. This condition plays a crucial role in determining the behavior of the internal energy ( ) of the gas.
Step 1: First Law of Thermodynamics. The First Law of Thermodynamics is given by the equation: where: - is the change in the internal energy of the system, - is the heat exchanged by the system, - is the work done by the system on the surroundings.
Step 2: Isothermal Process for an Ideal Gas. In an **isothermal process** for an ideal gas, the temperature is constant. Since the internal energy of an ideal gas depends only on temperature (and not on volume or pressure), the **change in internal energy** ( ) for an isothermal process is zero: Thus, applying this to the First Law of Thermodynamics: Rearranging this equation: This implies that the heat absorbed by the system is equal in magnitude to the work done by the system, but with the opposite sign.
Step 3: Work and Heat Direction. During the expansion of the gas: - The work ( ) done by the gas is positive because the gas is expanding and pushing against external pressure. - To maintain a constant temperature during this expansion, the gas must absorb heat ( ) equal in magnitude but opposite in sign to the work done, so .
Conclusion: Thus, in the case of an irreversible isothermal expansion of an ideal gas: Therefore, the correct answer is .

Concept: Thermodynamic properties are classified into two types:

• Extensive Properties: These depend on the amount of substance present. Examples: Mass, Volume, Internal Energy.
• Intensive Properties: These do not depend on the amount of substance. Examples: Temperature, Pressure, Density.

Thus, intensive properties remain the same regardless of system size.
Step 1: {Check each option based on property type.}

• Mass → Extensive property
• Volume → Extensive property

Therefore, option (A) is incorrect.
Step 2: {Evaluate the second option.}

• Density → Intensive property
• Temperature → Intensive property

Both are intensive properties.
Step 3: {Check remaining options.}

• Volume → Extensive
• Mass → Extensive

Since these options include extensive properties, they are incorrect. Hence, the correct pair containing only intensive properties is Density and Temperature.