Avertical piston-cylinder device contains water and is being heated on top of a range. during the process, 65 btu of heat is transferred to the water, and heat losses from the side walls amount to 8 btu. the piston rises as a result of evaporation, and 5 btu of work is done by the vapor. determine the change in the energy of the water for this process.

The change in energy=47 Btu

Explanation:

Given that

Heat transfer to the water=60 Btu

Heat loss from the walls=8 Btu

Work done by the system= 5 Btu

From first law of thermodynamics

   Q=ΔU+W

Here Q =Heat transfer

        ΔU=Change in internal energy

         W=Work transfer

From standard sing convention

if heat is added to the system then it will taker as positive and if  heat is escaping from the system then it will taker as negative.

If work is done by system then it will take as positive and if work is done on system then it will take as negative.

So net heat transfer in the system(Q)=60-8 Btu

                                                       Q =52 Btu

Work done by system(W)= 5 Btu

Now by putting the values

 Q=ΔU+W

52= ΔU+5

ΔU=47 Btu

So the change in energy=47 Btu

answer:

(b)

explanation: