Question Video: Identifying the Observations of the Reaction between Hydrochloric Acid and Sodium Carbonate Chemistry • Third Year of Secondary School

Video Transcript

A student adds a diluted solution of hydrochloric acid to a sample of Na2CO3 to detect the presence of CO3 2− ion. Which of the following is the correct observation? (A) Effervescence and evolution of CO2 gas. (B) Effervescence and evolution of CO gas. (C) Effervescence and evolution of H2 gas. (D) Formation of a white precipitate and evolution of CO2 gas. Or (E) formation of a white precipitate and evolution of CO gas.

To detect the presence of certain compounds or ions, qualitative tests that produce highly visible products can be used. In this question, we are using hydrochloric acid to detect the presence of carbonate ions, and we are asked what observation we would likely see.

When an acid reacts with a carbonate compound, a salt, carbon dioxide gas, and water are produced. So when hydrochloric acid is added to sodium carbonate, the aqueous salt, sodium chloride, is formed and we would observe effervescence due to the carbon dioxide gas bubbling through the solution. Therefore, the correct observation would be answer choice (A), effervescence and evolution of CO2 gas.