Organic chemistry is not the easiest of subjects, but one class at Ohio State University earned automatic full marks on their first test thanks to one sharp-eyed student.

Professor Christopher Callam had thrown a paper ball towards the back of the hall at the beginning of the lecture to review the Bronsted-Lowry theory of "donating a proton" for acid-base chemistry.

"The ball was a proton and after he threw it he said 'I just made an acid of myself' to help us remember it in the future," one student said.

Dr Callam then offered to give the entire class full marks on the first quiz if the person who had the ball could toss it into the trash can at the front of the hall, according to student Rachel Brown.

Student Vinny Forte, who Ms Brown had initially identified as "Benny", successfully made the shot — to the cheers of the lecture hall.

Dr Callam was also "really excited" for the students and was cheering with them, Ms Brown said — although he did end up adjusting his initial promise slightly.

According to students in the class, the original deal was there would be no quiz.

Instead the professor decided the class would still have to take the quiz, although the full marks would still be rewarded.

"He emphasised that we have to still show up for recitation to get the 100 on the quiz but he was happy for us," Ms Brown said.

She said she filmed the video because Dr Callam said someone made the shot last year but no-one had footage, she told Buzzfeed News.