Final answer:
The work required per unit mass of water when pumped from 50 kPa to 4.82 MPa cannot be directly calculated without the specific volume. For accurate results, one needs to refer to steam tables for the specific volume at the initial pressure and then use the formula Work = v × (P2 - P1).
Step-by-step explanation:
The student's question involves the work required per unit mass of water when it is pumped from a saturated liquid state at 50 kPa to a higher pressure of 4.82 MPa within a steam power plant. In thermodynamics, the work done on the system (in this case, water) by the pump can be calculated with the formula Work = v × (P2 - P1), where v is the specific volume of the fluid, P2 is the final pressure, and P1 is the initial pressure. However, since the problem statement does not provide the specific volume of saturated liquid water at 50 kPa, we can't directly calculate the work done per unit mass.
If the specific volume were known, the work could be calculated and expressed in kilojoules per kilogram (kJ/kg). For an accurate calculation, one would typically refer to steam tables to find the specific volume of the liquid at the given initial pressure.
Considering an example problem from the reference information provided, when steam does work on a piston, the work can be calculated by Work = Pressure × Area × Distance moved by the piston, or equivalently by Work = Force × Distance. These formulas highlight that when the pressure is constant, as it is in the given examples, the work output can be found by multiplying the constant pressure by the change in volume, which is the area of the piston times the distance it moves.