ENGR266 Summer 2019 Q A1[PARTIAL] Left out: Part (c) (9 marks: molar volume of hexane from the ideal gas law and the Pitzer generalised correlation for the second virial coefficient) is left out: the generalised (Pitzer) correlation is not in the current slides or formula sheets (CHECK in the audit).

Answer ALL parts (a) - (d)

Formulas you may need

• Wet-mixture properties: $v = (1 - x)v_f + x v_g$, $s = (1 - x)s_f + x s_g$, $x = m_g/m_{total}$ (on the formula sheet)
• Ideal gas law: $pV = nRT$ (on the formula sheet)
• Phase rule (triple point: $P = 3$, $C = 1$ gives $F = 0$): $P + F = C + 2$ (on the formula sheet)

1. (a)
   Sketch the temperature-entropy diagram below and label the solid, solid-liquid, solid-vapour, liquid, liquid-vapour and vapour regions. Also indicate the location of the critical point and the triple-point line.
   [8]
2. (b)
   Use the data-table provided in Appendix 1 - Thermodynamics for Chemical Engineering: Formula Sheet to calculate the entropy of 1,1,1,2-tetrafluroethane (HFC-134a) at $36^\circ\mathrm{C}$ with a volume of $0.0184\ \mathrm{m^3\,kg^{-1}}$.

   s =kJ/(kg K)Check
   [6]
3. (d)
   What are the two key approximations made in the ideal gas law?
   [2]Third