4)          At constant temperature, an ideal gas obeys Boyle's Law: PV = K, where K is a constant. A
             certain mass of ideal gas has a pressure of 150 kPa when its volume is 20 litres. (1 litre =
             10^-3 m³).

    (a)     Determine the value of the constant K.                                                                          (4)

   
(b)    The gas undergoes an isothermal expansion, as indicated below, a to b. How much work is
             done by the gas during this expansion ? [ln(1.5) = 0.4]                                                 (8)

            
Isothermal expansion means that T is constant, therefore,

   
(c)     If U_a = 30 J, assuming no change of state from a to b, what is U_b, and why ?              (2)

             Isothermal expansion U_a = U_b (no temperature change). U_b = 30 J

    (d)     How much heat enters or leaves the system during the process a to b, and why ?        (3)

             1^st law of thermodynamics

   
(e)     1000 J of work are done on the gas to take it from b to a via c. What is the pressure of the gas
             at c ?                                                                                                                            (4)

   
(f)     How much work is done by the gas during the complete cycle abca ?                 (4)