Water (10 kg/s) at 1 bar pressure and 50 c is pumped isothermally to 10 bar. what is the pump work? (use the steam tables.) o -7.3j/s o 7.3 kj/s o -210 kj/s o 3451 kj/s

Explanation:

For an isothermal process equation will be as follows.

                W = nRT ln

It is given that mass is 10 kg/s or 10,000 g/s (as 1 kg = 1000 g). So, calculate number of moles of water as follows.

                    No. of moles =

                                           =

                                           = 555.55 mol/s

                                           = 556 mol/s (approx)

As T = or (50 + 273.15) K = 323.15 K. Hence, putting the given values into the above formula as follows.

                  W = nRT ln[/tex]\frac{P_{1}}{P_{2}}[/tex]

                      =    

                     =    

                     = -3440193.809 J/s

Negative sign shows work is done by the pump. Since, 1 J = 0.001 kJ. Therefore, converting the calculated value into kJ as follows.

                          = 3440.193 kJ/s

                          = 3451 kJ/s (approx)

Thus, we can conclude that the pump work is 3451 kJ/s.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.