Hi i think the last person that solved this problem on here wasnt very clear so

Question

Hi i think the last person that solved this problem on here wasnt very clear so i reposted to see if someone else can give me a different direction. First i found the volume which is by using the saturated mixture table i found my values at 200 kpa for vf and vfg so that i can find the specific volume , i used the equation specific volume= vf+xvfg that result gave me the specifice volume to be.443 then i multiplied it by the mass to get the volume 4.43 m^3, and then i used the equation for work in a isobaric process W=P(V2-V1), P being the constant pressure 200 kpa, My second volume will be 3 times my first volume, i plugged the values in and got W=200(13.29 m^3 - 4.43 m^3) and the value i got 1772 KJ i am 100% sure this part is right, the next part i am having trouble with is finding the heat Q, I know what equation to use Q=m(u2-u1)+W i am multiplying by m because the u2 and u1 will be specifice internal energy because I am pretty sure you will have to use teh table to find the two u's and i know i can use the equation SPECIFIC INTERNAL ENGERY= uf+xufg and i just want regular internal energy so that i can combine the Work with it , my problem is i do not know what my u2 and u1 is i think i can find u1 but i dont know how to find u2 since they are both at the same pressure so it wouldnt make sense to use the same values for both u2 and u1, i kind of have an idea but not 100% sure so if someone can help find u2 and u1 i would greatly appreciate and correct me if i did any of these steps wrong, Here is the picture of the problem.

Explanation / Answer

Your first part is right.
Now second part.
You know your final volume which is triple of the original volume . Right ?

And you also know the mass of the mixture inside since it remains unchanged in expansion process. So you can calculate specific volume by doing volume/mass. This is your specific volume 2.

Now use the steam table. See the value of h (enthalphy) at this new specific volume 2 and 200 Kpa Isobar. take this as h2.

Search value of h1(enthalphy) for original specific volume 1 and 200Kpa isobar.

Now to calculate Q = m(h2-h1) .

The process you were following is also quite correct. Use steam table to find value of u1 for specific volume 1 and 200 Kpa and u2 for specific volume 2 and 200 Kpa. Plug the values and get the answer.

If you have any doubt ask in comments. Rate my answer wisely. Please.

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