Chemical Engineer Interview Questions

CHEMICAL ENGINEER SAMPLE INTERVIEW QUESTIONS

Question: What are some of the key qualities a chemical engineer has to possess to be able to do their job effectively?

Explanation: This is an example of an opening or general question. The interviewer will ask this type of question early in the interview to get you talking, learn a little bit about you, and discover information they can use for subsequent questions.

Example: “There are several qualities that make a chemical engineer effective in their work. The first and most important is attention to detail. Chemical engineers need to be aware of every detail of the projects they are involved with to get the results they are looking for and for safety purposes. Other characteristics include patience, perseverance, creative thinking, and flexibility. Another characteristic is the ability to collaborate with a diverse workforce.”

Question: What is flow control, and can you explain how it is used in a chemical engineering process?

Explanation: This is a technical question. As a chemical engineer, you can expect the majority of the interview will consist of technical and operational questions. In order to prepare for these questions, you should review the job posting and research the company and its operations. This may give you some clues as to the type of questions you will be asked.

Example: “Flow control is a process to manage the movement of a material through a production or distribution process. The objective of flow control is to optimize the material, equipment, and processes. As an example, I wouldn’t specify a piece of equipment with a capacity of 1000 units per hour if the projected production volume was only 500 units per hour. Flow control is managed using sensors and monitoring equipment placed at key points in the production process.”

Question: Can you explain the third law of thermodynamics?

Explanation: This is a technical question in which the interviewer is asking you to define a term used in your job. Technical questions are best answered by simply defining the term. Don’t embellish or provide any additional information. The interviewer will ask a follow-up question if they need more detail.

Example: “The third law of thermodynamics states that when a system reaches absolute zero, a minimum value is reached by the entropy of the system. In plain language, this means you can reduce the system to a static state in which no activity occurs by moving it to its relative value of absolute zero.”

Question: Can you explain the difference between unit operation and a unit process?

Explanation: This is an operational question in which the interviewer is trying to learn about your approach to this job and some of the processes and procedures you use to perform the necessary functions. Operational questions are best answered by walking the interviewer through the process.

Example: “The difference between unit operation and a unit process is very subtle. A unit operation refers to the changes which occur in the mass and concentration of the material when energy is provided from an external source and where no chemical change occurs ... think boiling water. On the other hand, a unit process refers to the change in the reactants present in the process resulting from a chemical reaction due to energy provided to the materials, usually in the form of heat. An easy way to visualize this is baking a cake.”

Question: What is material requirement planning, and how do you use this in your job as a chemical engineer?

Explanation: This is another operational question in which the interviewer is asking about a specific process you use in your job. A good way to answer operational questions is to define the term the interviewer was asking about and then provide an example of how it is used.

Example: “Material requirement planning is the process of estimating the amount of raw material required to produce a finished product.  The calculation involves not only the components but allowances for loss and waste during production. Several software applications make these calculations relatively easy and accurate. Material requirement calculations are typically part of the company’s MRP system.”

Question: What is the solvent?

Explanation: This is yet another technical question. The interviewer is likely to switch between operational and technical questions throughout the interview. Try not to let this throw you. You should be able to easily answer any of these questions based on your experience as a chemical engineer.

Example: “The basic definition of a solvent is that it is a liquid that can remove, dissolve, or suspend components of a material without any chemical change to the original material. Solvents are typically used as cleaners, carriers for the application of materials to a surface, or separate different materials. Typical solvents include water, alcohols, and other reactive liquids.”

Question: What are the three classes of an organic solvent?

Explanation: This is a follow up to the previous question. Any time you answer a question during an interview, you can anticipate there may be a follow-up question. The interviewer will ask these to dig deeper into a topic or clarify your previous answer.

Example: “The three classes of organic solvents are hydrocarbon, halogenated, and oxygenated. Typical oxygenated solvents include alcohol, ketones, and esters. Aromatics and aliphatics are hydrocarbon solvents. Halogenated solvents are usually chlorinated agents. Each of these is used for specific purposes and with materials they either do or don’t react with.”

Question: Can you explain the concept of a wet bulb globe temperature and how it is used?

Explanation: This is another operational question that is very specific to a chemical engineering process. We can’t emphasize enough how you need to prepare for interviews by performing a great deal of research about the company, its products, and the processes they are likely to be using. Answering your questions in the context of their business requirements will result in a better outcome for the interview.

Example: “A wet bulb globe temperature measures the sultriness of an environment. The measurement is based on the humidity, airspeed, and radiant temperature of an environment. When combined, each of these factors can dramatically affect chemical processes. This is an international standard which was developed over 50 years ago when it was found that a dry bulb temperature, which measures the ambient temperature of an environment, was found to be insufficient in the field of chemical engineering.”

Question: What are some of the considerations you need to know for a piping system that is used to transfer slurries?

Explanation: This operational question is very specific to the employer’s business and a process they use. If you are interviewing with a manufacturer that doesn't use slurries, you wouldn’t need to know about this particular process.

Example: “In addition to capacity, surface tension, and piping materials, the key consideration for piping systems used to transfer slurries is that they need to be able to self-drain. Since slurries generally contain solids and are heavier and denser than most liquids, being able to self-drain is critical. A related consideration is the amount of pressure required to blow out the line since blockages can easily occur.”

Question: What is an angle of repose, and why is it important within the chemical industry?

Explanation: This is another operational question, meant to test your knowledge of specific processes within the chemical engineering industry. Fortunately, chemical engineers typically focus on specific segments of the industry. Therefore, most of the questions you are asked should be related to your experience in your field of study. This makes them relatively easy to answer, assuming you’ve done your homework and prepared for the interview.

Example: “The angle of repose refers to how a conical pile forms when a solid material is poured onto a flat surface. The angle measured as that between the side of the pile and the surface it is being poured on to. Factors that contribute to how the pile forms include the surface area, the density of the material, and the material’s coefficient of friction. An easy way to visualize this is to picture sand being poured onto a surface versus a pile of rocks. The rocks will have a higher angle of repose because they tend to form a steeper pile.”

• Can you explain how the method of "powder coating" works?

• How can you separate hydrogen peroxide into hydrogen and oxygen?

• Have you ever delivered a project that was late? How was it received?

• What is one way to estimate the efficiency of a pump?

• What is a diluting agent? Explain it as if you were explaining it to someone who has no background in chemistry.