Chemical Engineering Multiple Choice Questions and Answers for freshers on “Differential Pressure Measurements”.

1. Which of the following is used for the pressure measurement of only liquid?

a) Manometer

b) Piezometer

c) Differential Manometer

d) None of the mentioned

Answer: b

Clarification: Piezometer is a pressure measuring device used to measure the pressure of liquid only.

2. Which of the following is used to measure a pressure of only gas?

a) U-tube manometer

b) Piezometer

c) Differential Manometer

d) None of the mentioned

Answer: a

Clarification: U-tube manometer is used to measure the pressure of gas only.

3. What is the difference between manometer and differential manometer?

a) Differential manometer has gas in empty space

b) Manometer has gas in empty space

c) Differential manometer has liquid in empty space

d) Manometer has liquid in empty space

Answer: a

Clarification: Differential manometer has gas in empty space while manometer has a vacuum.

4. Which of the following device is used to measure the velocity of flow?

a) Manometer

b) Venturi meter

c) Pitot tube

d) None of the mentioned

Answer: c

Clarification: Pitot tube is used to measure the velocity of flow.

5. A U-tube manometer is open at one end and has a gas at the other end if the level of the mercury in both legs of the manometer is equal then what is the temperature of the gas?

a) 1 Pa

b) 1 Torr

c) 1 mm Hg

d) 1 atm

Answer: d

Clarification: Since the level of mercury in both legs are equal, this means that pressure is equal on both ends, => pressure of gas = pressure of atmosphere = 1 atm.

6. A U-tube manometer is closed at both ends one end is vacuum and other end has a gas, if the difference in level of mercury is h = 10 mm, what is the pressure of gas?

a) 1.33 Pa

b) 1.45 Pa

c) 1.56 Pa

d) 1.75 Pa

Answer: a

Clarification: Since the other end of the manometer has vacuum, this means the pressure of gas is equal to the difference in pressure of mercury in both ends, => Pressure of gas = d*g*h = 13.6*9.8*0.01 = 1.33 Pa.

7. A closed U-tube manometer has a gas on one end with pressure 10 Pa and other end has vacuum, what is the approximate density of the liquid if the height difference of the liquid is 10 cm?

a) 1 Kg/m^{3}

b) 10 Kg/m^{3}

c) 100 Kg/m^{3}

d) 1000 Kg/m^{3}

Answer: b

Clarification: Pressure of gas = Pressure due to height difference of liquid = d*g*h, => 10 = d*10*0.1, => d = 10 Kg/m^{3}.

8. A closed U-tube manometer has a gas on one end with pressure 5 Pa and other end has vacuum, what is the approximate height difference of the liquid if the density of liquid is 10 Kg/m^{3}?

a) 5 mm

b) 10 mm

c) 50 mm

d) 100 mm

Answer: c

Clarification: Pressure of gas = Pressure due to height difference of liquid = d*g*h, => 5 = 10*10*h => h = 0.05 m = 50 mm.

9. A closed manometer is filled with 3 fluids first on the left leg with density 8 kg/m^{3} and length 10 cm, middle one with density 10 kg/m^{3} and height difference 5 cm more on right leg and the third on the right leg with density 15 kg/m^{3}, what is the length of the third liquid?

a) 1 cm

b) 2 cm

c) 3 cm

d) 4 cm

Answer: b

Clarification: Pressure on both legs should be equal, => 8*10 = 10*5 + 15*x, => x = 2 cm.

10. A barometer has liquid level 10 cm above the outside level and the gas captured inside has the pressure of 0.5 atm, what is the density of liquid?

a) 0.5 atm-s^{2}/m^{2}

b) 1 atm-s^{2}/m^{2}

c) 1.5 atm-s^{2}/m^{2}

d) 2 atm-s^{2}/m^{2}

Answer: a

Clarification: Pressure of gas + Pressure of liquid = atmospheric pressure, => 0.5 atm + d*10*0.1 = 1 atm, => d = 0.5 atm-s^{2}/m^{2}.

11. A barometer has liquid of density 1 kg/m^{3} of level 5 cm below the outside level, what is the pressure of the gas captured inside?

a) 0.5 atm + 1 Pa

b) 1 atm + 0.5 Pa

c) 1.5 atm + 1 Pa

d) 2 atm + 0.5 Pa

Answer: b

Clarification: Pressure of gas = Pressure of liquid + atmospheric pressure = 1*10*0.05 Pa + 1 atm = 0.5 Pa + 1 atm.

12. A barometer has liquid with density 1 Kg/m^{3}, and the gas has pressure 0.5 atm, what is the height of liquid level?

a) 0.01 atm-m^{2}-s^{2}/kg

b) 0.05 atm-m^{2}-s^{2}/kg

c) 0.1 atm-m^{2}-s^{2}/kg

d) 0.5 atm-m^{2}-s^{2}/kg

Answer: b

Clarification: Pressure of gas + Pressure of Liquid = atmospheric pressure, => 0.5 atm + 1*10*h = 1 atm, => h = 0.05 atm-m^{2}-s^{2}/kg.

13. A barometer the liquid-1 with density 2 Kg/m^{3} and height 5 cm below the outside level and above that liquid-2 with density 0.5 Kg/m^{3} and length 10 cm, what is the gauge pressure of the gas?

a) 0.01 Pa

b) 0.05 Pa

c) 0.1 Pa

d) 0.5 Pa

Answer: d

Clarification: Gauge pressure of gas + Pressure of liquid-2 = Pressure of liquid-1, => Gauge pressure of gas = 2*10*0.05– 0.5*10*0.1 = 0.5 Pa.

14. A barometer has liquid-1 with density 5 Kg/m^{3} and height 10 cm below the outside level above that there is liquid-2 of length 5 cm, if the gauge pressure of the gas is 1 Pa, what is the density of liquid-2?

a) 2 Kg/m^{3}

b) 4 Kg/m^{3}

c) 6 Kg/m^{3}

d) 8 Kg/m^{3}

Answer: d

Clarification: Gauge pressure of gas + Pressure of liquid-2 = Pressure of liquid-1, => 1 + d*10*0.05 = 5*10*0.1, => d = 8 Kg/m^{3}.

15. A barometer has liquid-1 with density 1 Kg/m^{3} and height 10 cm below the outside level above that a liquid-2, if the gauge pressure of gas is 0.5 Pa, what is the pressure liquid-2?

a) 0.5 Pa

b) 1 Pa

c) 1.5 Pa

d) 2 Pa

Answer: a

Clarification: Gauge pressure of gas + Pressure of liquid-2 = Pressure of liquid-1, => Pressure of liquid-2 = 1*10*0.1 – 0.5 = 0.5 Pa.

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