# 100+ Chemical Engineering Interview Questions and Answers

Today we will share Chemical Engineering Interview Questions and Answers if you want to crack your Chemical Engineering Interview then you need to read tghis post because we will share 100+ Chemical Engineering Interview Questions and Answers.

## Fluid Mechanics

1. Write down different types of pump name in according to its classification.
2. Draw Reynolds Number vs Friction factor to make moody’s flow diagram and show its different parameters.
3. Draw the characteristic curve of pump.
4. Comparison between the venturi meter and orifice meter.
5. Which one has higher hydraulic radius between circular and square shape pipe? Why?
6. When we use Hagen-Poiseuille’s equation?
7. Write down the working principle of orifice meter.
8. What is NPSH?
9. Write down the Navier-Strokes equation along with its uses, significance, range and conditions.
10. Draw a diagram of an Orifice meter.
11. Write Poiseuille’s equation and its application.
12. Convert 1 poise into English system.
13. Name and classify different types of pumps that are used in chemical process industry.
14. Water with 1 centipoise is flow in pipe with ID 10 cm. the volumetric flow rate was 2m3/min. Calculate the friction loss per length of pipe? (f=0.316/R)
15. The discharge of a centrifugal pump is proportional to – D/D2/D3/D4
16. Water of 1cp is flowing a pipe of 6 cm ID with 3.15 cubic meter per minute. Calculate the friction factor. (f=0.315R-0.25).
17. In practical point of view compare with orifice and venturi meter.
18. How does rotameter work and sketch it.
19. Sketch the characteristic curve of centrifugal pump.
20. What are the advantages and disadvantages of centrifugal pump over other pumps.
21.  What is NPSH? How temperature is affect on NPSH? Which is advantageous, either higher NPSH or lower NPSH, and why?
22. What is cavitation? What are the effect of cavitation? How to prevent cavitation?
23. Water (1000kg/m3) flows through a 60 cm diameter pipe at a rate of 100L/s and viscosity is 3.5×105 kg/m.s is the flow laminar or turbulent?
24. Explain different types of flow, temperature, pressure, and level measuring device.
25. Write down the classification of pump which is used in process industry.
26. Water with viscosity 1 CP flows through a steel pipe of 10 cm diameter with 2 m3/min. What will be the frictional head loss per meter? Given f=0.362×(1/R0.25)
27. Water flows through the system shown below at a rate of 20L/min. Estimate the pressure required at point 1 if frictional loss is negligible.
28. What is cavitation of a pump? What do you mean by NPSH? Why it is necessary for a pump?
29. Difference between density and specific gravity.
30. What is the function of compressor? Write about the types of compressor.
31. What do you mean by centerline velocity?
32. Given Z1=350ft, Z2=25ft, Q=2000ft3/min. Find the power delivered by the pump.
33. Differentiate between NPSHr and NPSHa.
34. How can you prevent surging of compressor?
35. How flow characteristics can be changed in a same pump?
36. A figure was given in which a siphon tube of 5cm diameter was dipped in a tank with height 5m. A nozzle of 3cm diameter is present at the tube end of the siphon. From the liquid surface of the tank (C) the siphon tube goes vertically to point (D), then point D to E is horizontal and then the point E to the ground G. CD distance is 3m. Asked to find the pressure at point C and D.
37. Mention each symbol of Bernoulli’s equation.
38. Bernoulli and manometer related math
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## Heat Transfer

1. Related math about, Q (Heat loss) = kA
2. 1-2 pass shell and tube heat exchanger temperature
3. In a 2m diameter pipe heat exchanger 140oC steam condenses at 110oC. the cold water passes through the exchanger from 15oC to 10oC in counter current direction. What is the LMTD of the heat exchanger?
4. Write an empirical equation for forced convection heat transfer and write the meaning of each term.
5. Draw the temperature profile for Co-current and Counter-current flow.
6. What are the different heat exchanger used in a process industry?
7. Given a double pipe heat exchanger ID=2cm and outer diameter 4cm. Oil is cooled from 90oC to 10oC which is passing through inner tube. Water with 30oC is used to cool oil and final temperature is 35oC (i) What is the heat transfer coefficient including (ho, h1)? (ii) Write the Numerical value for calculating NRL. (iii) Calculate log mean temperature difference if flow is countercurrent.
8. Water of 300oF is to be cooled to 200oF by cooling water of 100oF whose final temperature becomes 120oF. For heat transfer in this condition which one is to be used between parallel and counter current flow and why?
9. Define critical thickness of insulation.
10. Define dirt factor of shell and tube heat exchanger.
11. Draw the temperature profile of double pipe heat exchanger.
12. A furnace which is made of brick (75mm thickness) is covered with 6.4mm steel plate. The inside temperature of furnace is 647oC and outside air temperature is 27oc. Given, kbrick=1.1W/m.oC, ksteel=39W/m.oC, ho=68W/m2.oC. Calculate the heat loss per unit area of the furnace wall.
13. [Heat transfer related math] [k1, k2, ho, T1, To, thickness was given and asked for calculating the heat transfer per unit area]
14. Increase in no. of passes in heat exchanger increases the pressure drop and heat transfer co-efficient. Is it true? Explain.
15. What is the importance of fin type heat exchanger?
16. A thick-walled tube of stainless steel (18% Cr, 8% Ni, k=19W/moC) with 2cm inner diameter (ID) and 4cm outer diameter (OD) is covered with 3cm layer of asbestos insulator (k=o.2W/mo.C). The inside wall temperature of the pipe is maintained at 600oC and outside wall temperature of the pipe is maintained at 100oC. (i) Calculate the heat loss per meter of length. (ii) Calculate the tube-insulation interface temperature.

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## Material Balance

1. Stock gas sample CO (60%), CO2 (28%), N2 (5%), balance O2 in dry basis. In a test H2O mole fraction 0.10, what is wet basis stock gas composition?
2. 250 kg NaCl is reacted with 260 kg 98% H2SO4, and volatile components are dried off. What should be the composition of final solid component?
3. A potassium ore contains 70% KCl, 20% NaCl and 10% inert. After evaporation and crystallization, the ore contain 98% KCl and 2% NaCl. What amount of ore are required to produce 1 metric ton final product?
4. Wastewater contains 40mg/L TSS. This water is discharged in a river with a flow rate of 10 L/min, the flow of river was 15 L/min. What is concentration of TSS in river?
5. One ton salt containing 3% moisture and 800kg sulfuric acid of 95% pure is feed to a reactor. The reaction mass is heated to vaporize volatile matter and moisture. Calculate the composition of solid mass.
6. Total naphtha (10000L, sp gr 0.72) is feed to a column. Three products: a) Light naphtha (6000L, sp gr 0.67), b) Heavy naphtha (4000L, sp gr 0.74), c) Stream gas. Calculate the composition of gas stream.
7. 1000kg solution of sulfuric acid contains 30% of H+/kg. A mixture of 23% HCl and 37% H2SO4 is to be produced. How much sulfuric acid does it need to make the mixture?
8. 1000kg of 15% solution of sodium sulfate is being evaporated. For making 140kg of Na2SO4.10H2O and a mother solution of 30%, How much water has been evaporated?
9. What is theoretical air and excess air?
10. SI unit of dynamic viscosity is poise. Convert 1 poise to English unit.
11. An ore containing 86% KCl, 10% NaCl, and Further information??
12. One hundred mol/h of butane and 5000 mol/h of air are feed into a combustion reactor. Calculate the percent of excess air.
13. A mixture contains 40% solute (salt) and another mixture contains 30% salt. To produce a 1250 kg of 35.5% salt final solution, which amount of mixtures have to be mixed?
14. A hydrocarbon gas is burned with air. The dry-basis product gas composition is 1.5 mole% CO, 6 mole% CO2, 8.2 mole% O2, and 84.3 mole% N2. There is no atomic oxygen in the fuel. Calculate the ratio of hydrogen to carbon in the fuel gas and speculate on what the fuel might be. Then calculate the percent excess air fed to the reactor.
15. A stack gas contains 60 mole% N2, 15 mole% CO2, 10 mole% O2, and the balance H2O. Calculate the molar composition of gas on a dry basis.
16. Math related to calculation of molar volume and molar density of ideal gas.
17. Gasoline(SG??) and kerosene (SG=0.82) are blended to obtain a mixture with a specific gravity of 0.78. Calculate the volumetric ratio (volume of gasoline/volume of kerosene) of the two compounds in the mixture, assuming Vblend= Vgasoline+ Vkerosene
18. Methane burns in the reactions-

1) CH4 + 2O2 = CO2 + 2H2O

2) CH4 + 1.5O2 = CO + 2H2O

One hundred mol/h of methane is fed to a reactor. What is the theoretical air flow rate assuming that only 70% of the methane reacts?

1. Draw a phase diagram and label various points in that diagram.

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## Energy Balance

1. A gas weight 26 gm, 51 gm and 15 gm of CH4, C2H6, C3H8 has a volume of 5L. Find the pressure at NTP of 30oC.
2. 100 m/h feed NG contains 90% CH4, 10% C2H6, 2.5% excess air. Calculate the air flow rate and the composition of gas. If reaction proceeded theoretically, then could any change the adiabatic flame temperature? Why?
3. A natural gas contains 85% CH4 and 15% C2H6 by volume. The heat of combustion of CH4 and C2H6 at 25oCand 1atm with water vapor as the assumed product are given below-

1) CH4 + 2O2 = CO2 + 2H2O(v), ∆HL = -802 KJ/mol

2) C2H6 + 7/2 O2 = 2CO2 + 3H2O (v), ∆HC = -1428KJ/mol

## Calculate the higher heating value (KJ/g) of the natural gas.

• Given, Ꝭ=10Kg/cm2, V=1cm3, T= 30oC and R=8.314. What is the mass of gas where composition is 80% CH4, 15% C2H4, 5% N2?
• 5g Hydrogen and 80g Methane are contains in a 40 L cylinder. If the temperature of this cylinder is 70oC, what is the pressure of this cylinder?
• The calorific value of 1kg of coal with ash content of 22% is 1200KJ/kg. For complete combustion of coal 12 kg air is needed. What is amount of flue gas when 5kg coals were burned?
• 10g of hydrogen and 30g of nitrogen placed in a cylinder of 5L and temperature is 50oC. What is the total pressure of the cylinder?
• Equimolar of hydrogen and helium have been mixed. 50g of the mixture is taken in a container of 20L. A gauge connected to the container reads the pressure 2 atm. What is the temperature of the container? (MW of hydrogen is 1g and helium 4g)
• 5g hydrogen and 8g oxygen are mixed in a 20L container. What will be the pressure of container if temperature is 190oC?
• The specific internal energy of helium at 300K and 1 atm is 3800J/mol, the specific volume at the same temperature and pressure is 24.63L/mol. Calculate the enthalpy of helium at this temperature and pressure, and the rate at which enthalpy is transported by a stream of helium at 300K and 1atm with a molar flow rate of 250kmol/h.
• 10L/min of water is to be heated from 15oC to 65oC as it flows through a 5m long tube of ID 3cm. The tube is equipped with an electric resistance heater that provides uniform heating throughout the surface of the tube. Given properties at bulk mean temperature: Ꝭ=992Kg/m3, k=0.63W/m.oC, Cp = 4200j/kg.oC, Pr =4.3, Find the inner surface temperature of the pipe exit.
• A gas was analyzed and found 88% v/v of methane, 10% v/v of water. Find the HHV and LHV of the gas stream. [At 25oC and 1atm, Heat combustion of methane and ethane are respectively 880kj/mol and 1559.5kj/mol, and the heat of vaporization of water is 44kj/mol]
• A fuel containing 88% of methane (v/v), 7% of ethane (v/v), 2% of propane (v/v) and 3.5% of nitrogen. Find the HHV and LHV of the fuel. After complete combustion, carbon dioxide (g), nitrogen (g) and water (l) were obtained. (Heat of combustion and heat of vaporization will be given)
• At 25oC and 1atm, the following reaction occurs:

C4H10 + 6.5O2 = 4CO2 + 5H2O, ∆HC = -2658kj/mol

Then,

1) Is the reaction endothermic or exothermic?

2) Is heat required to remove or add in the reactor?

3)Find the LHV of n-butane vapor.

Process Safety Engineering

1. What is minimum pipe diameter? What is threshold limit value (TLV)?
2. Write the ten personal protective equipment (PPE) for process industry like KAFCO.

## Environmental Engineering

1. How will you minimize the corrosiveness of boiler feed water? Write a list of the checking parameters for demineralized water used for boiler feed water.

## Process Control

1. Draw the block diagram of the feed backward system and write down its working features.
2. Feedback loop and work of each component.
3. How can you keep π = K by PI and PID? Explain.
4. What will be the response of a unit step change for (i) P controller and (ii) PI controller?
5. For a water treatment plant, the addition of alkali/acid is needed to keep the pH around 7. For this condition, draw a P and I logic block diagram.
6. Briefly describe forward and backward control feed.
7. Draw, discuss and differ feedback and feed-forward control loop.
8. Principle of cascade control and its block diagram.
9. Derive the equation of PI controller.
10. Write down the function of: pressure relief valve, blowdown valve, shutdown valve, gas detector, heat detector, flame detector.
11. What is thermocouple? Why is it used?
12. List essential elements of Robust automatic control to be used for typical chemical process.
13. Write the action/effect of PID controller when a disturbance occurs. Explain elaborately.
14. Define the hardware of control system and explain the suitability of feedback and feed forward control system.
15. Define distributed control system.
16. Draw the control system in a three-phase separator.
17. Differentiate between PI and PID controller.
18. What are the advantages and disadvantages of integral and derivative controller?
19. In compressor station, why emergency shutdown (ESD) system is required?

## Process Design

1. Cooling water inlet = 34°C, outside air = 34°C, is it cool water?
2. Write down the mechanism of cooling tower.

Analytical Chemistry

1. Anometer Check it?? is used for
2. Find the molarity of 0.967 molal aqueous solution of a compound. Molecular weight is given, and the density of solution is 1.24/mL.
3. pH of the acid HA is 6.16. Find pKa of the acid.
4. 0.5 mg of Benzene is added in a 250mL hexane solution. The solution gives peak at 260mm in a 1cm cell and absorbance is 0.2. Find the molar absorptivity.

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Corrosion Engineering

1. Why should gas moisture be removed? How do corrosion and (CH4 +H2O) cause blockage?
2. Corrosion prevention (Cathodic and Anodic) with related figure, stray current effect, underground pipeline protection, corrosion rate, and types of corrosion (ex. Crevice corrosion).
3. What is cathodic protection? Describe impressed current cathodic protection.
4. Write the precaution measures to prevent pipelines (from inside and outside) from corrosion.
5. Describe the general working mechanism of cathodic protection.
6. Write different types of corrosion and explain cathodic protection.
7. Show that, corrosion of metals in extractive metallurgy is reverse.
8. Compare between and explain anodic and cathodic protection. Loss of cathodic protection made it possible of saving miles of pipelines in transportation of natural gas, how?
9. Why does polarization occur? What happens to the electrodes during polarization?
10. Corrosion case study at interface/fitting point of Zn-Cu in underground water pipe.
11. Explain cathodic protection of pipelines with proper sketch.

## Process Technology

1. Write down the name of raw material and reaction involved in urea fertilizers manufacturing process.
2. What is annealing?
3. Urea is produced from natural gas. Give the five important chemical reaction with section name for urea production process through ammonia production.
4. What are the desired products of natural gas reforming? To perform reactions usually primary and secondary reformers are used. There is a reformer which combines both reformers. What is the name of the reformer? What is the function of it?
5. Draw a block diagram for chemical recovery in paper and pulp process.

## Fuel and Energy

1. Define:  Flash point, pour point.
2. Predict the effects when liquid fuel and gaseous fuel are burnt in insufficient air.
3. Can CNG be used in cooking? Why?
4. Rearrange according to their calorific value: LNG, Coal, LPG, H2, CNG.
5. Arrange according to the increasing boiling point: LPG, Naphtha, Heavy Fuel, Diesel, Petrol and Kerosene.

## Mass Transfer

1. 2 MS এ র মাধ্যমে কিভাবে moisture separate করা হয়? Question??
2. What is steam economy of evaporation.
3. Write and explain the Henri’s Law and Raoult’s law.
4. Write the significance of Schmidt number.
5. What is absolute humidity, relative humidity, and percentage humidity?
6. What is dew point and wet bulb temperature?
7. Write the principle and industrial application of pressure swing absorption.
8. Write the physical significance of Sherwood number and Schmidt number.
9. Figure??

a) Which is fed tray?

b) The fed is saturated liquid, saturated vapor, or vapor liquid mixture?

c) The temperature at point 6 is lower, higher, or as same as point 1?

1. State Fick’s Law and write down its application.
2. McCabe Thiele method related theory and math
3. Maximum velocity and mass flux related math.
4. Antoine equation related math [Given data: P, y4, ys and values of A, B & C of Antoine equation. Find out the dew point of C4 and C5 mixture]
5. Write the differences between evaporation and distillation.
6. At elutriation stage of crystallization, presence of crystals is visible. If water is pump towards upward direction, the velocity of water will be less than the terminal velocity of the coarse crystal. Explain why?
7. In distillation column, fed is 100kg/h which contains 60% methanol and 40% water. The desired top product contains 90% and bottom product contains 10% of methanol. [operating lines were given] Find the height of column where the tray efficiency is 60% and spacing between each tray is 1.5ft.
8. In a three-effect evaporator, steam enters at 110oC. The final solution boils at 56oC. Assume the solution rises negligible above boiling point. The heat transfer coefficients for the three effects are 2500W/m2 .0C ,2000 W/m2 .0C and 2000 W/m2 .0C. Further information??

## Chemical Reaction Engineering

1. A reversible reaction (2A = Y + 2Z) proceeds in a 5 dm3 volume flask. The reaction starts with 4 mole of A and 1 mole of remains at the equilibrium. Find Kc.
2. H2 + Br2 = 2HBr. The change of Br is -0.001 mole in 0.01s at a 0.25L flask. Find d /dt.
3. Write down the Arrhenius equation? Why is this equation used? Mention its parameters name.
4. For two equal volumes of CSTR the conversion is –
5. More than when they are connected in series
6. More than when they are connected in parallel
7. Equal when they are connected in series
8. Less than when they are connected in series
9. Find out the volume of CSTR for 99% conversion.

## Natural Gas and Petroleum Reservoir

1. Normally gases are saturated with water from mines and then dried off before entering the pipeline, why? What is the process to do so?
2. Raw natural gas bears moisture. Write an established process to move out the moisture from the gas.
3. Why mercaptan is added in natural gas??
4. Draw a schematic flow diagram of natural gas processing.
5. List out the equipment used in natural gas processing from well to the house of the customers.
6. In a natural gas processing, why condenser is used before an absorption tower and heater is used before a stripper?

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