250+ TOP MCQs on Chemical Clarification and Answers

Environmental Engineering Multiple Choice Questions on “Chemical Clarification”.

1. Which of the following represents the coagulant pipe in the following figure?

Figure: Flash mixer
a) A
b) B
c) C
d) D
Answer: a
Clarification: ‘A’ represents the coagulant pipe which is used for discharging the coagulant into the flash mixer.

2. Which of the following represents the device which is used for sludge removal in the following figure?

Figure: Flash mixer
a) F
b) E
c) D
d) B
Answer: c
Clarification: ‘D’ represents the drain valve which is used for the removal of sludge from the mixer.

3. _________ is the average of velocities at a point over a definite period of time.

Figure: Flash mixer
a) Mean velocity
b) Relative velocity
c) Velocity gradient
d) Temporal mean velocity
Answer: d
Clarification: Temporal mean velocity is the average of velocities at a point over a definite period of time. It is represented by G.

4. Which of the following goes to the flocculation tank in the following figure?

Figure: Flash mixer
a) B
b) C
c) E
d) F
Answer: b
Clarification: ‘B’ represents the outlet of the mixer which goes to the flocculation tank.

5. Which of the following is the correct expression regarding temporal mean velocity in the following figure?

Figure: Flash mixer
a) G = (P/μV)^1/2
b) G = (P/μV)
c) G = (P/μV)²
d) G = (Pμ/V)^1/2
Answer: a
Clarification: Temporal mean velocity G = (P/μV)^1/2, where P is the power, μ is the dynamic viscosity and V is the volume of the tank. It is measured in per second.

6. Which of the following is correctly paired in the following figure?

Figure: Flash mixer
a) C – Impeller
b) D – Outlet
c) F – Deflecting wall
d) E – Impeller
Answer: d
Clarification: E represents the Impeller which is driven by the electric motor to revolve in the tank.

7. The speed of impeller in a flash mixer is ___________

Figure: Flash mixer
a) 45rpm
b) 60rpm
c) 110rpm
d) 200rpm
Answer: c
Clarification: The speed of impeller in a flash mixer is between 100 to 120 rpm and the propeller type impeller is used.

8. ‘C’ in the following figure represents the ________

Figure: Flash mixer
a) Impeller
b) Impeller shaft
c) Deflecting wall
d) Flash mixer wall
Answer: c
Clarification: ‘C’ represents the deflecting wall, whereas the boundary below the inlet and outlet of the tank is the flash mixer wall.

9. The detention period of a flash mixer is _________________

Figure: Flash mixer
a) 2 minutes
b) 30 minutes
c) 1 hour
d) 2 hours
Answer: a
Clarification: The detention period of flash mixer lies between 30 seconds to 2 minutes.

10. Which of the following represents the impeller shaft in the following figure?

Figure: Flash mixer
a) F
b) E
c) C
d) B
Answer: a
Clarification: Impeller is connected to impeller shaft which is further connected to electric motor so as to drive the impeller and mixing of coagulant in water takes place.