Thermodynamics

Heat and work are examples of path functions because they depend on the path taken by the system.

Internal energy and entropy are state functions as their values depend only on the current state of the system, not on the process used to reach that state.

Step 1: Apply first law of thermodynamics.
where = heat interaction, = work input.

Step 2: Substitution.
Here, (rejected heat), .

Final Answer:

Step 1: Understanding the fugacity concept.
For ideal gases, the fugacity approaches the pressure as pressure approaches zero. The ratio of fugacity to pressure tends to 1, which is unity.

Step 2: Explanation of options.
- (B) Unity is the correct answer as the ratio of fugacity to pressure approaches 1 for an ideal gas as pressure approaches zero. - (A) Zero would not apply here, as the fugacity and pressure are proportional at low pressures. - (C) Infinity is not correct, as the ratio approaches 1, not infinity. - (D) The ratio does not have an indeterminate value at low pressures.

Final Answer:

Step 1: Understanding the process.
In a piston-cylinder arrangement, when the system is heated by placing it on the top of a burner, the volume of the gas is allowed to expand and the pressure remains constant. This is typical for a constant pressure process.

Step 2: Explanation of options.
- (A) A constant pressure process occurs when the gas expands and is heated. - (B) A constant volume process would not allow the gas to expand. - (C) An adiabatic process would involve no heat exchange, which is not the case here. - (D) An isothermal process would involve constant temperature, which is not described here.

Final Answer: