Thermodynamics Vapor Tables Problem


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> **3-29** A piston-cylinder device contains $\pu{0.85 kg}$ of refrigerant-134a at $\pu{-10^\circ C}$. The piston that is free to move has a mass of $\pu{12 kg}$ and a diameter of $\pu{25 cm}$. The local atmospheric pressure is $\pu{88 kPa}$. Now, heat is transferred to refrigerant-134a until the temperature is $\pu{15^\circ C}$. Determine (**a**) the final pressure, (**b**) the change in the volume of the cylinder, and (**c**) the change in the enthalpy of the refrigerant-134a.  
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> [![enter image description here](https://i.stack.imgur.com/dLolK.png)](https://i.stack.imgur.com/dLolK.png)
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This is my work so far...


[![enter image description here](https://i.stack.imgur.com/BEXL3.png)](https://i.stack.imgur.com/BEXL3.png)


These are the superheated R-134a vapor tables that are given: 


[![enter image description here](https://i.stack.imgur.com/hQIcp.png)](https://i.stack.imgur.com/hQIcp.png)




I got the same answer that the book got. Linear interpolation on v like you did is not accurate enough. You expect the behavior to be close to that of an ideal gas. So pv should be nearly constant. Try interpolating on pv rather than on v and see what you get. 


At p=0.06, pv=0.021029


At p=0.1, pv=0.020743


So, at p = 0.0904, pv=0.020812


v=0.020815/.0904 = 0.2302


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