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.

Answer 1

Answer:

Explanation:

Carbon dioxide CO₂ is an acidic gas.

Most oxides of non-metals are acidic gases and they behave like a true acid in solution. They have all properties of an acid in this regard.

When CO₂ solution is formed, a carbonic acid is produced. This is a weak acid:

        CO₂ + H₂O ⇄ H⁺ + HCO₃⁻

Answer 2

Answer:

The incorrect about reasoning is that there is hydrogen ion present in the solution of dissolved carbon dioxide in water.

Explanation:

The acid ph is less than 7.

If we have a solution of carbon dioxide it means we have dissolved carbon dioxide gas in water and this leads to reaction of carbon dioxide gas with water to produce carbonic acid.

$CO_{2}+H_{2}O--->H_{2}CO_{3}$

This carbonic acid formed dissociates into carbonates and proton.

The formation of proton (hydronium ion) results the acidic pH of the solution.

$H_{2}CO_{3}--->H^{+}+HCO_{3}^{-}$

$HCO_{3}^{-}-->H^{+}+CO_{3}^{-2}$