Chemical Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Before your Chemical Engineer interview, it helps to see the questions from the interviewer's side. We have picked eight from our set of 25 and added the reason each one gets asked.

Eight Chemical Engineer interview questions, and what the interviewer is thinking

1. Why did you choose chemical engineering, and what does a typical day as a process engineer on a plant involve?

Why they ask: To test motivation and a realistic picture of the role.

2. Talk me through how you would set up a mass and energy balance for a continuous process unit.

Why they ask: To check core process engineering fundamentals.

3. What do you look for when you review a P&ID, and what information does it show?

Why they ask: To see if the candidate can read the key process engineering document.

4. How is a shell-and-tube heat exchanger sized, and what causes fouling and how do you manage it?

Why they ask: To check heat transfer design knowledge.

5. Explain the principles of distillation and how reflux ratio affects separation and cost.

Why they ask: To check unit operations knowledge.

6. Product yield on your unit has dropped by three per cent over the past fortnight, and nobody knows why. How would you investigate?

Why they ask: To test structured process troubleshooting.

7. Tell me about a time you optimised or improved a chemical process, and what the results were.

Why they ask: To check delivery of measurable improvement.

8. What are the differences between a CSTR and a plug flow reactor, and how would you choose between them?

Why they ask: To test reactor design fundamentals.

A sample answer to question 1

Why did you choose chemical engineering, and what does a typical day as a process engineer on a plant involve?

I was drawn to chemical engineering because it covers chemistry, physics, maths and economics, and applies them to making things at scale that people actually use. On a manufacturing site, a typical day starts with reviewing overnight data and any deviations with the operations team. I'd then work on a mix of tasks: troubleshooting a process issue, analysing yield or energy data, supporting a modification through the management of change process, or checking a P&ID update. I'd also attend a production meeting and spend time on the plant talking to the operators, because they notice things that data doesn't show. I enjoy that the work goes from calculations in an office to standing next to a vessel, and that small improvements can save a lot of money or reduce emissions.

Common mistake to avoid: Giving a purely academic answer; describing only desk-based work

Want the rest?

Full model answers, key points and common mistakes for all 25 questions are on the Chemical Engineer interview questions page. The first five are free, no sign-up needed.