LPG gas is a fuel source used in areas without natural gas lines. Assume that LPG may be modeled as a mixture of propane and n-butane. Since the pressure of the LPG tank varies with temperature, there are safety and practical operating conditions that must be met. Suppose the desired maximum pressure is 0.7 MPa, and the lower limit on desired operation is 0.2 MPa. Assume that the maximum summertime tank temperature is 50°C, and that the minimum wintertime temperature is -10°C.

(a) What is the upper limit (mole fraction) of propane for summertime propane content?

(b) What is the lowest wintertime pressure for this composition from part (a)?

(c) What is the lower limit (mole fraction) of propane for wintertime propane content?

(d) What is the highest summertime pressure for this composition from part (b)?