National Institute of Technology 2007 Mid-term IVSem - Question Paper

Mid-term IVSem
CET-1 Marks: 50 Time: 1.30hrs
1. 1. Write a pote on specific heat and why is the Cp always greater than Cv ? (4)
2. Five kilogram of CO2 gas is contaiped in a piston cylinder assembly at a pressure of
7.5bar and a temperature of 300K. The piston has a mass of 6000kg and surface area of
1m2 The friction of the piston on the walls is significant and cannot be ignored. The
atmospheric pressure is 1.01325 bar. The latch holding the piston in position ?s suddenly
removed and the gas is allowed to expand. The expansion is arrested when the quantity
is double the origipal quantity. Determine the work done in the surroundings. (4)
3. One kilogram of air is heated reversibly at constant pressure from an initial state of 300K
and 1bar until its quantity triples. compute W, Q, change in internal energy and enthalpy
for the process. presume that air obeys ideal gas legal regulations and that Cp =29moG1 K'1 (4)
4 An rigid and insulated tank of 3m3 quantity is divided into 2 compartments and compartment of quantity 1m3 contains an ideal gas at 0.1 Mpa and 300K while the 2nd compartmept of quantity 2m3 contains the identical gas at 1Mpa and 100K.lf the partition ranging from the 2 compartments is ruptured, determine the final state(T and P) of the gas
(4)
5. Derive an formula for 1st legal regulations of thermodynamics for flow process. (6)
6. Explain the Carnot principle. (4)
7. Calculate the COP of a refrigerator and a Carnot heat pump if both the devices are
operating ranging from the reservoirs at –10C and 40C. (2)
8 State and prove the Clausius inequality. ( 5)
9. The latent heat of fusion at 0°C and the latent heat of vaporisation at 100°C for water are
333.43kJ/kg and 2257 kJ/kg respectively. compute a) the entropy change if 1 kg ice
at 0°C is converted into liquid water at 0C by exposing the ice to the ambient atmosphere
at 30°C, b) the entropy change if 1 kg liquid water at 100°C is completely at the identical
temperature by heating with a bunsen flame. (2)
10)State mathematically the principle of the increase in entropy and hence show that "the
entropy of the universe is increasing". (5)
11. Ope mole of nitrogen (gamma=1.4) at 0.1MPa and 300K has been subjected to a series
of processes as a outcome of which it reached the state P=0.5MPa and 600K. Determine
the change in the entropy of nitrogep and it may be treated as an ideal gas. (5)
12. A 5 kilogram steel block at 100C is quenched in 5 kilogram water at 30C in an open
container. compute the entropy change of steel, water and the universe. The specif?c
heat capacity of steel is 0.5kJ/kg.K and latent heat of water 2257 kJ\kg K
hf(100°C)=419.04 kJ/kg.K, h,(30°C)=125.79 kJ/kg.K, Sf(100°C)=1.3069 kJ/kg.K ,
Sf(30°C)=0.4369 kJ/kg.K , Sg(100°C)= 7.3549 kJ/kg.K

Earning:   Approval pending.