The boys were among nine Dubbo Christian School and five MAGS students to complete the three-hour exam.

Yesterday's exam covered topics such as corrosion, solubility, hydrocarbons, acids and bases and nuclear chemistry.

Andy said he did not study extensively, but came out of the exam feeling confident.

"I'm happy with how the exam went," he said.

"I think it was fair if not slightly easy."

The aspiring engineer said chemistry is his favourite subject and only had issues with one question.

He found after the exam he had answered the troublesome question correctly though.

Ben said he had studied a bit for the exam and he came out of it "slightly confident, but not as confident as Andy."

"I found it more difficult, I wouldn't say it was easy," he said.

But overall Ben said it was an "enjoyable subject" to study.

Ben plans to take a gap year and go to Thailand with his family before studying electrical engineering.