Question

Four kilograms of carbon monoxide (co) is contained in a rigid tank with a volume of 1 m3. the tank is fitted with a paddle wheel that transfers energy to the co at a constant rate of 14 w for 1 h. during the process, the specific internal energy of the carbon monoxide increases by 10 kj/kg. if no overall changes in kinetic and potential energy occur, determine (a) the specific volume at the final state, in m3/kg. (b) the energy transfer by work, in kj. (c) the energy transfer by heat transfer, in kj, and the direction of the heat transfer.

Answer 1

Part (a): Specific volume
Specific volume, v = V/m, V = Volume of the tank, m = mass of CO in the tank
Therefore,
v = 1/4 = 0.25 m^3/kg

Part (b): Energy transferred in kJ
Work done, W = PΔt, where P = power = 14 W = 14 J/s, t = time = 1 hour = 60*60 = 3600 seconds
Therefore,
W = 14*3600 = 50400 J = 50.4 kJ

Part (c): Energy transferred by heat
ΔU = Q + W
Then,
Heat transferred by heat, Q = ΔU - W
But, ΔU = mΔu = 4 kg*10 kJ/kg = 40 kJ
Therefore,
Q = 40 - 50.4 = -10.4 kJ (negative sign indicates that heat is removed from the CO).