Steam expansion: calculating piston work from internal energy change

[kawf]

Homework Statement

A mass of 5 kg of steam is contained within a piston cylinder assembly. The steam undergoes an expansion from its initial state with e1 = 3000 kJ/kg to its final state with e2 = 2500 kJ/kg. During the process there is a heat transfer of 80 kJ to the steam. Also, a paddle wheel transfers 10 kJ of work to the steam. Calculate the amount of energy transfer by work from the steam on the piston during the process.

Homework Equations

dE = del Q - del W

The Attempt at a Solution

Would this be correct?
W = del Q - dE
= (80kJ + 10kJ) - (2500 kJ/kg - 3000 kJ/kg)
W = 590 kJ

I don't believe this is correct but it's all I have been able to come up with so far. Any guidance is appreciated

 

[Maxim Zh]

e1 and e2 are specific energies. Multiply them by the steam mass.

You can not sum [kJ] and [kJ/kg].

Watching the dimensions in formulas is a great way to verify your solution.

 

[kawf]

sorry for my half asleep attempt...

e1 and e2 are specific energies. Multiply them by the steam mass.

You can not sum [kJ] and [kJ/kg].

Watching the dimensions in formulas is a great way to verify your solution.

so after multiplying the steam mass buy each of the energies would I just take the difference?

such that:

m*e2 - m*e1

(5kg)(2500 kJ/kg) - (5kg)(3000kJ/kg) = -2500 kJ

 

[Maxim Zh]

Yes, you would.

$$\Delta E = m(e_2 - e_1).$$

By the way, the solution in the first post (after the correction) will give you the work done by the piston on the steam. But if I see it right the question is about the opposite value.