A change in state involving a decrease in entropy can be spontaneous, only if ____________________?

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. For spontaneous changes in an isolated system (S = entropy) ___________________?

   A. ds = 0
   B. ds <0
   C. ds > 0
   D. ds = Constant

3. 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

4. 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 ?

   A. Δ H = 0 and ΔS = 0
   B. Δ H ≠ 0 and ΔS = 0
   C. Δ H ≠ 0 and ΔS ≠ 0
   D. Δ H = 0 and ΔS ≠ 0

5. The absolute entropy for all crystalline substances at absolute zero temperature is ____________________?

   A. Zero
   B. Negative
   C. More than zero
   D. Indeterminate

6. During a reversible isothermal expansion of an ideal gas, the entropy change is___________________?

   A. +ve
   B. 0
   C. -ve
   D. ∞

7. The expression for entropy change given by, ΔS = – nR ln (P2/P1), holds good for___________________?

   A. Expansion of a real gas
   B. Reversible isothermal volume change
   C. Heating of an ideal gas
   D. Cooling of a real gas

8. Entropy change in case of reversible adiabatic process is________________?

   A. Minimum
   B. Zero
   C. Maximum
   D. Indeterminate

9. The entropy change in a reversible isothermal process, when an ideal gas expands to four times its initial volume is_________________?

   A. R loge 4
   B. R log10 4
   C. Cv log10 4
   D. Cv loge 4

10. Entropy change of mixing two liquid substances depends upon the_________________?

    A. Molar concentration
    B. Quantity (i.e. number of moles)
    C. Both A. and B
    D. Neither A. nor B