High pressure steam is expanded adiabatically and reversibly through a well insulated turbine, which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ΔH and ΔS respectively for this process ?

Related Mcqs:

1. Steam undergoes isentropic expansion in a turbine from 5000 kPa and 400°C (entropy = 6.65 kJ/kg K) to 150 kPa) (entropy of saturated liquid = 1.4336 kJ/kg. K, entropy of saturated vapour = 7.2234 kJ/kg. K) The exit condition of steam is_______________?

   A. Superheated vapour
   B. Partially condensed vapour with quality of 0.9
   C. Saturated vapour
   D. Partially condensed vapour with quality of 0.1

2. 1m3 of an ideal gas at 500 K and 1000 kPa expands reversibly to 5 times its initial volume in an insulated container. If the specific heat capacity (at constant pressure) of the gas is 21 J/mole . K, the final temperature will be ?

   A. 35 K
   B. 174 K
   C. 274 K
   D. 154 K

3. A solid metallic block weighing 5 kg has an initial temperature of 500°C. 40 kg of water initially at 25°C is contained in a perfectly insulated tank. The metallic block is brought into contact with water. Both of them come to equilibrium. Specific heat of block material is 0.4 kJ.kg-1. K-1. Ignoring the effect of expansion and contraction and also the heat capacity to tank, the total entropy change in kJ.kg-1, K-1 is_________________?

   A. -1.87
   B. 0
   C. 1.26
   D. 3.91

4. A system undergoes a change from a given initial state to a given final state either by an irreversible process or by a reversible process, then (where, Δ S1 and Δ SR are the entropy changes of the system for the irreversible and reversible processes respectively) ?

   A. Δ S1 is always Δ SR
   C. Δ S1 is always > Δ SR
   D. Δ S1 is always = Δ SR

5. Entropy change of the reaction, H2O (liquid) → H2O (gas), is termed as the enthalpy of___________________?

   A. Solution
   B. Vaporisation
   C. Formation
   D. Sublimation

6. Enthalpy of formation of NH3 is – 46 kJ/kg mole. The enthalpy change for the gaseous reaction, 2NH3 → N2 + 3H2, is equal to _____________ kJ/kg. mole?

   A. 46
   B. 92
   C. -23
   D. -92

7. A closed system is cooled reversibly from 100°C to 50°C. If no work is done on the system________________?

   A. its internal energy (U) decreases and its entropy (S) increases
   B. U and S both decreases
   C. U decreases but S is constant
   D. U is constant but S decreases

8. For a constant pressure reversible process, the enthalpy change (ΔH) of the system is___________________?

   A. Cv.dT
   B. Cp.dT
   C. ∫ Cp.dT
   D. ∫ Cv.dT

9. Enthalpy change resulting, when unit mass of solid is wetted with sufficient liquid, so that further addition of liquid produces no additional thermal effect, is called the heat of________________?

   A. Mixing
   B. Adsorption
   C. Wetting
   D. Complete wetting

10. A steam carrying pipeline is insulated with two layers of insulating materials with the inferior insulation material forming the inner part. If the two insulating layers are interchanged, the heat conducted will____________________?

    A. Increase
    B. Decrease
    C. Remain unaffected
    D. May increase or decrease; depends on the thickness of each layer