As stated in the question: I have PV(T) [J/kg] vs P [Pa] plotted for 2 different temperatures. I'm to approximate the the temperatures using the lines and the ideal gas law. Note: V is the specific volume. I have no clue how to do this: I know that PV vs P is just as if I had nRT vs P. From this the temperature should be obtainable, however the slopes of the lines are negative, so I don't see how I should approach this. The pressure varies from 0 to 10^6 Pa and the PV varies from about 310600 to 306600 J giving a slope of about -0.004. I also had been given the information that the weight is 0.018kg/mole.