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Engineering :: Mass Transfer


51.  The Lewis number is the ratio of
A. thermal diffusivity to mass diffusivity B. mass diffusivity to thermal diffusivity
C. mass diffusivity to momentum diffusivity D. momentum diffusivity to thermal diffusivity

52.  Lewis number plays an important role in problems of
A. heat transfer only B. mass transfer only
C. simultaneous heat and mass transfer D. momentum transfer only

53.  Relative volatility ? for a binary system
A. decreases with increase in pressure B. increases with increase in pressure
C. increases with increase in temperature at constant pressure D. has no significance in distillation operation

54.  Relative volatility ? for a binary system is a measure of separability by distillation. If ? = 1 the separation by distillation is
A. maximum possible B. least possible
C. impossible D. optimum possible

55.  If y* = x the relative volatility ? for a binary system is always
A. zero B. one
C. infinity D. one except at x = 0 or 1

56.  To separate a binary mixture the relative volatility should be
A. equal to one B. less than one
C. greater than one D. greater than zero

57.  Component A is said to be more volatile than component B if for all temperature in the closed interval TA < T < TB.
A. the vapour pressure of A is less than the vapour pressure of B B. the vapour pressure of A is more than the vapour pressure of B
C. the vapour pressure of A is equal to 1 atm D. the vapour pressure of A is equal to the vapour pressure of B

58.  A two-phase is said to be in physical equilibrium if
A. the temperature of the vapour phase is equal to the temperature of the liquid phase B. the total pressure throughout the vapour phase is equal to the total pressure throughout the liquid phase
C. the tendency of each phase is exactly equal to its tendency to escape from the vapour phase to the liquid phase D. all of the above

59.  The normal boiling points of benzene and toluene are 80.1?C and 110.6?C respectively. A mixture containing 50 mole per cent benzene and 50 mole per cent toluene will boil at 1 atm at
A. 80.1?C B. 110.6?C
C. a temperature in between 80.1?C and 110.6?C D. a temperature of more than 110.6?C.

60.  Ethanol-water solution containing 50 mole per cent ethanol can be separated to get 97 mole per cent ethanol by
A. atmospheric distillation B. distillation at higher pressures
C. vacuum distillation D. all of the above




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