Chemical Engineering Diploma Interview Questions & Answers | EngineerX
Chemical Engineering (Diploma / Polytechnic) Interview Questions & Answers — commonly asked polytechnic diploma interview and campus placement questions with clear, practical answers. Tap any question to open its answer.
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Chemical Engineering — Diploma Interview Q&A
Q1What is Chemical Engineering?
AnswerChemical Engineering is a branch of engineering that deals with the design, operation, control, and optimization of industrial processes in which raw materials are converted into useful products through chemical, physical, and biological processes.
Q2What does a Chemical Engineer do?
AnswerA Chemical Engineer works with processes, equipment, materials, energy, and safety systems used to manufacture products. Their responsibilities may include process operation, production, quality control, process optimization, troubleshooting, equipment selection, and safety management.
Q3What is a chemical process?
AnswerA chemical process is a series of controlled operations in which raw materials undergo physical or chemical changes to produce a desired product. Examples include refining petroleum, manufacturing fertilizers, producing polymers, and treating water.
Q4What is process engineering?
AnswerProcess engineering involves designing, operating, controlling, and improving industrial processes. It focuses on achieving the required production rate, quality, safety, energy efficiency, and cost-effectiveness.
Q5What is a unit operation?
AnswerA unit operation is a basic physical step used in a chemical process, such as filtration, distillation, drying, evaporation, mixing, sedimentation, or heat transfer. A complete industrial process is usually made up of several unit operations.
Q6What is a unit process?
AnswerA unit process is an operation involving a chemical reaction or chemical transformation, such as oxidation, reduction, hydrogenation, nitration, polymerization, or neutralization.
Q7What is the difference between unit operation and unit process?
AnswerA unit operation mainly involves physical changes such as separation or heat transfer, while a unit process involves a chemical reaction or chemical transformation.
Q8What is mass balance?
AnswerMass balance is the application of the principle of conservation of mass to a process. It relates the mass entering, leaving, accumulating, and being generated or consumed within a process system.
Q9What is the basic equation of mass balance?
AnswerThe general mass balance is: Accumulation = Input − Output + Generation − Consumption. For a steady-state process without reaction, accumulation and generation or consumption are zero, so input equals output.
Q10What is steady-state operation?
AnswerA process is said to operate at steady state when important process variables such as flow rate, temperature, pressure, and composition remain essentially constant with time at a particular location in the system.
Q11What is a batch process?
AnswerA batch process is an operation in which a specific quantity of raw material is charged into equipment, processed for a defined period, and then removed as a batch. It is commonly used when flexibility or smaller production quantities are required.
Q12What is a continuous process?
AnswerIn a continuous process, raw materials are continuously fed into the system and products are continuously removed. Continuous processes are commonly used for large-scale production where stable operating conditions and high throughput are required.
Q13What is the difference between batch and continuous processes?
AnswerA batch process handles material in individual lots, while a continuous process continuously feeds and removes material. Batch operation generally provides greater flexibility, whereas continuous operation is often suitable for high-volume production.
Q14What is a flow rate?
AnswerFlow rate is the quantity of fluid passing through a specified point per unit time. It can be expressed as mass flow rate, such as kg/s, or volumetric flow rate, such as m³/s.
Q15What is mass flow rate?
AnswerMass flow rate is the mass of a substance flowing through a particular section per unit time. It is commonly expressed in kg/s, kg/h, or tonnes/h.
Q16What is volumetric flow rate?
AnswerVolumetric flow rate is the volume of fluid flowing through a particular section per unit time. Common units include m³/s, m³/h, and litres/minute.
Q17What is density?
AnswerDensity is the mass of a substance per unit volume. It is commonly expressed in kg/m³ and is an important property used in flow, equipment sizing, and process calculations.
Q18What is viscosity?
AnswerViscosity is a measure of a fluid's resistance to flow or deformation. A high-viscosity fluid flows more slowly under the same driving conditions than a low-viscosity fluid.
Q19What is the difference between dynamic and kinematic viscosity?
AnswerDynamic viscosity represents a fluid's resistance to shear flow, while kinematic viscosity is the ratio of dynamic viscosity to fluid density. Dynamic viscosity is commonly expressed in Pa·s and kinematic viscosity in m²/s.
Q20What is pressure?
AnswerPressure is the normal force exerted per unit area of a surface. In chemical plants, pressure is an important process variable that affects flow, reaction, boiling, separation, and equipment operation.
Q21What is absolute pressure?
AnswerAbsolute pressure is pressure measured relative to a perfect vacuum. It is related to gauge pressure by adding the local atmospheric pressure to the gauge pressure.
Q22What is gauge pressure?
AnswerGauge pressure is the pressure measured relative to the surrounding atmospheric pressure. Most industrial pressure gauges display gauge pressure unless specifically designed otherwise.
Q23What is vacuum?
AnswerVacuum is a condition in which the pressure of a system is below atmospheric pressure. Vacuum operation can be used for processes such as evaporation, distillation, drying, and certain material handling applications.
Q24What is temperature?
AnswerTemperature is a measure related to the thermal state of a substance and indicates the direction of heat transfer between bodies. It is commonly measured in degrees Celsius, Kelvin, or Fahrenheit.
Q25What is heat?
AnswerHeat is energy transferred between systems because of a temperature difference. In chemical processes, heat transfer is important in heating, cooling, evaporation, condensation, and reaction control.
Q26What is the difference between heat and temperature?
AnswerTemperature describes the thermal state of a substance, while heat is energy transferred due to a temperature difference. Temperature is a property of the system, whereas heat describes energy transfer.
Q27What is heat transfer?
AnswerHeat transfer is the movement of thermal energy from a region of higher temperature to a region of lower temperature. The three basic modes are conduction, convection, and radiation.
Q28What is conduction?
AnswerConduction is heat transfer through a material due to molecular interaction and temperature gradients, without bulk movement of the material.
Q29What is convection?
AnswerConvection is heat transfer between a surface and a moving fluid. It can occur naturally due to density differences or be forced using equipment such as pumps and fans.
Q30What is radiation?
AnswerRadiation is heat transfer through electromagnetic waves and does not require direct physical contact between the heat source and receiving surface.
Q31What is a heat exchanger?
AnswerA heat exchanger is equipment used to transfer heat between two or more fluids at different temperatures, generally without directly mixing them.
Q32What are common types of heat exchangers?
AnswerCommon types include shell-and-tube heat exchangers, plate heat exchangers, double-pipe heat exchangers, air-cooled heat exchangers, and spiral heat exchangers.
Q33What is a shell-and-tube heat exchanger?
AnswerA shell-and-tube heat exchanger consists of a bundle of tubes enclosed within a shell. One fluid flows through the tubes while another flows around the tubes inside the shell, allowing heat transfer between them.
Q34What is fouling in a heat exchanger?
AnswerFouling is the unwanted accumulation of deposits such as scale, dirt, corrosion products, or biological material on heat-transfer surfaces. It reduces heat-transfer efficiency and can increase pressure drop.
Q35What is the purpose of a cooling tower?
AnswerA cooling tower removes heat from circulating water by transferring heat to the atmosphere, mainly through evaporation. It is commonly used to cool process water in industrial plants.
Q36What is a boiler?
AnswerA boiler is equipment used to transfer heat to water and produce steam or hot water under controlled conditions. Steam may be used for heating, power generation, or industrial processes.
Q37What is steam?
AnswerSteam is water in the gaseous state. In chemical industries, steam is widely used for heating, evaporation, stripping, sterilization, and power generation.
Q38What is condensation?
AnswerCondensation is the change of a substance from vapour to liquid, usually accompanied by the release of latent heat.
Q39What is evaporation?
AnswerEvaporation is the removal of a solvent from a solution by vaporization, commonly using heat. It is frequently used to concentrate solutions.
Q40What is distillation?
AnswerDistillation is a separation process based primarily on differences in the volatility or boiling behaviour of components in a mixture. It involves vaporization followed by condensation.
Q41What is a distillation column?
AnswerA distillation column is equipment used to separate components of a liquid mixture based on differences in volatility. It contains internal devices such as trays or packing that promote contact between rising vapour and descending liquid.
Q42What is reflux in distillation?
AnswerReflux is the portion of condensed overhead liquid that is returned to the distillation column. It improves vapour-liquid contact and generally increases separation performance.
Q43What is a condenser?
AnswerA condenser is equipment that removes heat from a vapour to convert it into a liquid. Condensers are commonly used in distillation, refrigeration, and process cooling systems.
Q44What is a reboiler?
AnswerA reboiler is a heat-transfer device used to vaporize part of the liquid at the bottom of a distillation column. The generated vapour rises through the column and supports the separation process.
Q45What is filtration?
AnswerFiltration is a separation process in which a fluid passes through a porous medium while suspended solid particles are retained by the filter medium.
Q46What is centrifugation?
AnswerCentrifugation is a separation technique that uses centrifugal force to separate components with different densities, such as solids from liquids or different liquid phases.
Q47What is sedimentation?
AnswerSedimentation is a separation process in which suspended particles settle under gravity because of their density difference from the surrounding fluid.
Q48What is absorption?
AnswerAbsorption is a mass-transfer operation in which one or more components of a gas mixture are transferred into a liquid phase. It is commonly used for gas purification and removal of specific components.
Q49What is adsorption?
AnswerAdsorption is a surface phenomenon in which molecules from a gas or liquid accumulate on the surface of a solid or, in some cases, another phase. Materials such as activated carbon and molecular sieves are commonly used as adsorbents.
Q50What is the difference between absorption and adsorption?
AnswerAbsorption involves the transfer of a substance into the bulk of another phase, whereas adsorption involves the accumulation of a substance mainly on the surface of another material.
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