A student is deciding which chemicals are acids by measuring their pH. He sees that a solution of CO2 has an acidic pH. He decides that he must have contaminated his sample. He thinks that CO2 could not create hydrogen ions in the solution since it contains no hydrogen atoms. Explain what is incorrect about the student’s reasoning.

I kind of get the question but I don't know how to answer it fully. And I know the student is wrong because it react to water from what I've researches so far.

Question

A student is deciding which chemicals are acids by measuring their pH. He sees that a solution of CO2 has an acidic pH. He decides that he must have contaminated his sample. He thinks that CO2 could not create hydrogen ions in the solution since it contains no hydrogen atoms. Explain what is incorrect about the student’s reasoning.

 I kind of get the question but I don't know how to answer it fully. And I know the student is wrong because it react to water from what I've researches so far.