Question

When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?
A. No reaction takes place.
B. A colourless and odourless gas is released with brisk effervescence.
C. A brown coloured gas is released with brisk effervescence.
D. Formation of bubbles of a colourless and odourless gas.

Answer 1

When sodium bicarbonate reacts with the acetic acid it gives the sodium salt of acetic acid, water and carbon dioxide gas. Sodium carbonate is represented by the formula $NaHCO_3$ and acetic acid is represented as $CH_3COOH$.

Complete answer:
By the reaction of an acid with sodium bicarbonate, the aqueous sodium salt of the acid, and carbon dioxide gas forms.
The reaction of sodium bicarbonate and acetic acid is as follows:
${\text{NaHC}}{{\text{O}}_{\text{3}}}\, + {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\, \to \,{\text{C}}{{\text{H}}_{\text{3}}}{\text{COONa}}\,\,{\text{ + }}\,\,{{\text{H}}_2}{\text{C}}{{\text{O}}_3}$
The reaction of acetic acid with sodium bicarbonate, gives aqueous sodium acetate and carbonic acid. The carbonic acid is highly unstable so, it decompose to give water and carbon dioxide as follows:
${{\text{H}}_2}{\text{C}}{{\text{O}}_{\text{3}}}\, \to \,\,{{\text{H}}_2}{\text{O}}\,\,{\text{ + }}\,{\text{C}}{{\text{O}}_2}$
This carbon dioxide gas is released out of the test –tube which is observed in the form of brisk effervescence.
So, a colourless and odourless carbon dioxide gas is released with brisk effervescence when you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder.

Therefore, option (B) A colourless and odourless gas is released with brisk effervescence, is correct.

Note: The carbon dioxide is a colourless and odourless gas. So, only the brisk effervescence can be seen which confirms the evolution of the gas. As the carbon dioxide evolves the lime water converts into milky which also confirms the evolution of the gas.