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.