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

Related Mcqs:

1. Pure aniline is evaporating through a stagnant air film of 1 mm thickness at 300 K and a total pressure of 100 KPa. The vapor pressure of aniline at 300 K is 0.1 KPa. The total molar concentration under these conditions is 40.1 mole/m3. The diffusivity of aniline in air is 0.74 × 10-5m2/s. The numerical value of mass transfer co-efficient is 7.4 × 10-3. Its units are_______________________?

   A. m/s
   B. cm/s
   C. mole/m2.s.Pa
   D. k.mole/m2.s.Pa

2. Saturated solution of benzene in water is in equilibrium with a mixture of air and vapours of benzene and water at room temperature and pressure. Mole fraction of benzene in liquid is xB and the vapour pressures of benzene and water at these conditions are pv B and pv w respectively. The partial pressure of benzene in air-vapour mixture is_________________?

   A. PvB
   B. xB.PvB
   C. (Patm – Pvw)xB
   D. xB.Patm

3. 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

4. One kg of saturated steam at 100°C and 1.01325 bar is contained in a rigid walled vessel. It lias a volume of 1.673 m3. It cools to 98°C; the saturation pressure is 0.943 bar ; one kg of water vapour under these conditions has a volume of 1.789 m3. The latent heat of condensation (kJ/kg-1 ) under these conditions is___________________?

   A. 40732
   B. 2676
   C. 2263
   D. 540

5. The vapour pressure of water is given by, in Psat = A – (5000/T), where A is a constant, Psat is the vapour pressure in atm. and T is the temperature in K. The vapor pressure of water in atm. at 50°C is approximately__________________?

   A. 0.07
   B. 0.09
   C. 0.11
   D. 0.13

6. A vessel of volume 1000 m3 contains air which is saturated with water vapour. The total pressure and temperature are 100 kPa and 20°C respectively. Assuming that the vapour pressure of water at 20°C is 2.34 kPa, the amount of water vapour (in kg) in the vessel is approximately ?

   A. 17
   B. 20
   C. 25
   D. 34

7. Under conditions of equal reduced pressure and equal reduced temperature, substances are said to be in the ‘corresponding states’. At equal reduced conditions i.e., at the corresponding state, the ____________ of different gases are nearly the same?

   A. Compressibility
   B. Molecular weight
   C. Humidity
   D. None of these

8. A car tyre of volume 0.057 m3 is inflated to 300 kPa at 300 K. After the car is driven for 10 hours, the pressure in the tyre increases to 330 kPa. Assume air is an ideal gas and Cv for air is 21 J/mole.K. The change in the internal energy of air in the tyre in J/mole is__________________?

   A. 380
   B. 630
   C. 760
   D. 880

9. The maximum adiabatic flame temperature of fuels in air is ____________ the maximum flame temperature in pure oxygen?

   A. Lower than
   B. Higher than
   C. Same as
   D. Not related to

10. Air at a temperature of 20°C and 750 mm Hg pressure has a relative humidity of 80%. What is its percentage humidity? Vapour pressure of water at 20°C is 17.5 mm Hg?

    A. 80.38
    B. 80
    C. 79.62
    D. 78.51