Question Set 25

Question No. 1

Difference between Boiling Point and Melting Point.

Answer:

(A) The melting point is a defined for solids when it transfers from solid state to liquid state.

(B) The boiling point is defined for liquids for a state change from liquid to gas.

(C) Boiling point is highly dependent on the external pressure whereas the melting point is independent of the external pressure.

Question No. 2

State Laws of conservation of energy?

Answer:

According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.”

Question No. 3

Is the boiler a closed system?

Answer:

Yes definitely the boiler is a closed system.

Question No. 4

What is Carnot engine?

Answer:

It was being designed by Carnot and Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency.

Question No. 5

What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle?

Answer:

When liquid refrigerant as obtained from condenser is throttled, there are some vapours. These vapours if carried through the evaporator will not contribute to refrigerating effect. Using a flash chamber at some intermediate pressure, the flash vapour at this pressure can be bled off and fed back to the compression process. The throttling process is then carried out in stages. Similarly compression process is also done in two separate compressor stages.

Question No. 6

Why pistons are usually dished at top?

Answer:

Pistons are usually hollowed at top to

(A) Provide greater space for combustion

(B) Increase surface for flue gases to act upon, and

(C) Better distribution of stresses.

Question No. 7

What is the function of thermostat in cooling system of an engine?

Answer:

Thermostat ensures optimum cooling because excessive cooling decreases the overall efficiency. It allows cooling water to go to radiator beyond a predetermined temperature.

Question No. 8

Which formula forms a link between the Thermodynamics and Electro chemistry?

Answer:

Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and electromagnetism.

          ∆Hs/R = [∂ ln.p /∂(1/T)] (x)

Where: x – mole fraction of CO₂ in the liquid phase

p – CO₂ partial pressure (kPa)

T – Temperature (K)

R – Universal gas constant

α – mole ratio in the liquid phase (mole CO₂ per mole of amines)

Question No. 9

What is Hess Law?

Answer:

According to the Hess law the energy transfer is simply independent of the path being followed.

If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

Question No. 10

Which has more efficiency: Diesel engine or Petrol engines?

Answer:

Off course Diesel engine has the better efficiency out of two.