Practice Pakistan's most useful MCQs for competitive exams

When the gas to be dissolved in liquid is a/an ___________________ then normally co-current adsorber are used?

• (A)  Mixture of two gases
• (B)  Pure gas
• (C)  Ideal gas
• (D)  Sparingly soluble gas

Answer

Submitted By :Ali Uppal

Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 × 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is _________________________?

• (A)  5.6 × 10-4
• (B)  8.5 × 10-4
• (C)  5.6 × 10-3
• (D)  8.5 × 10-3

Answer

Submitted By :Ali Uppal

H2S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H2S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in meters) corresponding to an operating line given by, y = 5x + 0.001 is ______________________?

• (A)  2.0
• (B)  1.56
• (C)  1.0
• (D)  0.56

Answer

Submitted By :Ali Uppal

Large scale drying of sugar is done in a _______________ dryer?

• (A)  Spouted bed
• (B)  Tray
• (C)  Rotary
• (D)  Truck

Answer

Submitted By :Ali Uppal

With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop___________________?

• (A)  Decreases
• (B)  Remains unchanged
• (C)  Increases
• (D)  Decreases exponentially

Answer

Submitted By :Ali Uppal

A natural draft cooling tower is filled with wooden grids, which covers about _________________ percent of the tower height?

• (A)  10-15
• (B)  30-40
• (C)  70-80
• (D)  90-100

Answer

Submitted By :Ali Uppal

The Knudsen diffusivity is proportional to (where, T = absolute temperature) ______________________?

• (A)  √T
• (B)  T2
• (C)  T
• (D)  T4

Answer

Submitted By :Ali Uppal

Which of the following processes is not an example of adsorption applied to gaseous separations ?

• (A)  Recovery of valuable solvent vapors from dilute mixture with air and other gases
• (B)  Dehumidification of air and gas
• (C)  Removal of objectionable odour and impurities from industrial gases
• (D)  Decolouration of yellow glycerine

Answer

Submitted By :Ali Uppal

The cooling effect in a cooling tower can be speeded up by _______________________?

• (A)  Increasing the air velocity and area of exposed wet surface
• (B)  Reducing the barometric pressure
• (C)  Reducing the humidity of the air
• (D)  All

Answer

Submitted By :Ali Uppal

To remove all the moisture from a wet solid it requires exposure to _____________ air?

• (A)  Perfectly dry
• (B)  Highly humid
• (C)  High temperature
• (D)  None of these

Answer

Submitted By :Ali Uppal