1. The Concentration of the two phases in a closed system at the Interphase is
a) Changes continuously
b) Never changes
c) Becomes zero
d) Increases till the driving force becomes zero
Explanation: The concentration changes only if the component of the two phases added or removed. Generally, Interphase occurs at equilibrium. Once the additional component is added to a system at equilibrium, the concentration changes till it become uniform but it will be differ from the previous.
2. Diffusion of components between the phases at equilibrium is
a) Zero
b) Infinity
c) Changes continuously
d) Diffusion never occurs
Explanation: At equilibrium, the concentration becomes uniform so the rate of diffusion stops.
3. The real driving force of the mass transfer is
a) Chemical potential
b) Physical potential
c) Pressure gradient
d) Concentration gradient
Explanation: Chemical potential represents the dynamic equilibrium of the mass transfer.
4. According to Lewis and Whitman theory, the departure from concentration equilibrium at the Interphase is due to
a) Low mass transfer rates
b) High mass transfer rates
c) Moderate mass transfer rate
d) None of the mentioned
Explanation: Theoretically proved by Lewis and Whitman, that if the mass transfer rates are higher the concentration deviates from equilibrium.
5. The equilibrium concentrations in the gas and the liquid phases, in mole fraction, give rise to a curve known as
a) Equilibrium distribution curve
b) Equilibrium concentration curve
c) Differential distribution curve
d) Differential concentration curve
Explanation: The equilibrium distribution curve represents the phase-phase equilibrium curve with the coordinates of mole fractions in both the phases.
6. In a certain process, there is a variation in the driving force between the phases, such a process is
a) Batch process
b) Semi-batch process
c) Continuous process
d) Isothermal process
Explanation: In a batch process, concentration changes with time results in varying in driving force.
7. In a concurrent process, the entering and leaving stream of the liquid phase concentrations in terms mole ratio is 0.25 and 0.45 also the entering and leaving stream concentration of the gas phase in terms mole ratio is 0.4 and 0.6. Find the slope of the operating line.
a) 1
b) 2
c) 3
d) 4
Explanation: -Ls/Gs= 0.6-0.4/(0.45-0.25)
= 1.
8. Assume an ideal solution with pure component A, has a vapour pressure of 300 mmHg and the total pressure of 1atm. The concentration in terms of mole ratio is
a) 0.65
b) 0.28
c) 0.39
d) None of the mentioned
Explanation: According to Rauolt’s law, for an ideal solution
Total pressure= concentration x vapour pressure
Concentration in mole fraction=300/760 =0.39
Concentration in mole ratio = 0.39/(1-0.39)=0.65.
9. The operating line will be straight if its concentrations are represented in mole ratio
a) True
b) False
Explanation: The non- diffusing solute remains same throughout the process. So there is a straight operating line.
10. If the whole liquid and gas flow rates are same, we can use the mole fraction for getting a straight operating line
a) True
b) False
Explanation: If the flow rates are same, the non- diffusing solvent rates also same as the normal flow rate. So it is possible to use mole fraction for the representation of the operating line.