During a phase change process like sublimation, vaporisation, melting etc., the specific ____________ does not change?

Related Mcqs:

1. For water evaporating into unsaturated air under adiabatic conditions and at constant pressure, the ____________ remains constant throughout the period of vaporisation ?

   A. Dry bulb temperature
   B. Wet bulb temperature
   C. Humidity
   D. Relative saturation

2. The heats of vaporisation of CS2, C2H5OH &H2O are 26.8, 38.6 & 40.6 KJ/kg.mole respectively. The order of decreasing inter-molecular forces in these liquids is________________?

   A. H2O > C2H5OH > CS2
   B. CS2 > C2H5OH > H2O
   C. H2O > CS2 > C2H5OH
   D. CS2 > H2O > C2H5OH

3. The value of Trouton’s ratio (λb/Tb) for a number of substances is 21 (where, λb = molal that of vaporisation of a substance at its normal boiling point, KCal/kg. mole and Tb = normal boiling point, °K). The Kistyakowsky equation is used for calculation of Trouton’s ratio of _____________ liquids?

   A. Polar
   B. Non-polar
   C. Both A. & B.
   D. Neither A. nor B.

4. At 100°C, water and methylcyclohexane both have vapour pressures of 1 atm. Also at 100°C, the latent heats of vaporisation of these compounds are 40.63 kJ/mole for water and 31.55 kJ/mole for methylcyclohexane. The vapour pressure of water at 150°C is 4.69 atm. At 150°C, the vapour pressure of methylcyclohexane would be expected to be_________________?

   A. Significantly less than 4.69 atm
   B. Nearly equal to 4.69 atm
   C. Significantly more than 4.69 atm
   D. Indeterminate due to lack of data

5. The forces causing the vaporisation of liquid are derived from the Kinetic energy of translation of its molecules. The heat of vaporisation_________________?

   A. Increases with pressure rise
   B. Decreases with increasing pressure
   C. Becomes zero at the critical point
   D. Both B. & C.

6. Carborundum used for making crucibles for melting non-ferrous metals is chemically________________?

   A. Silicon carbide
   B. Silicon nitride
   C. Crystalline magnesia
   D. Zirconium sulphate

7. Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except______________?

   A. Cost
   B. Electrical conductivity
   C. Thermal conductivity
   D. Fusion point

8. The vapor pressure of a substance, at its melting point, is _____________ in the solid state as compared to that in the liquid state?

   A. Less
   B. More
   C. Same
   D. Either A. or B.; depends on the nature of the substance

9. Specific gravity on API scale is given by the relation (where, G = specific gravity at 15.5°C) ?

   A. °API = 200(G – 1)
   B. °API = (141.5/G) – 131.5
   C. °API = (140/G) – 130
   D. °API = 145 – (145/G)

10. In case of vapor-liquid equilibria, which of the following does not account for gas phase deviation from ideality ?

    A. Use of equation of state
    B. Fugacity co-efficient
    C. Activity co-efficient
    D. None of these