Question

When, you add Sodium hydrogencarbonate to Acetic acid in a test tube, a gas liberates immediately with a brisk effervescence. Name this gas. Describe the method of testing this gas.

Answer 1

• When Ethanoic acid reacts with Carbonates and Hydrogen carbonates, it produces Carbon dioxide gas, salt, and water.
• When Ethanoic acid reacts with Sodium bicarbonate, Sodium acetate is usually produced as a salt, as shown in the reaction below.$$\begin{gathered} {\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{l}\right)+{\mathrm{NaHCO}}_3\left(\mathrm{s}\right)\to {\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right) \\ \mathrm{Ethanoic}\mathrm{Sodium}\mathrm{Sodium} \\ \mathrm{acid}\mathrm{hydrogencarbonate}\mathrm{acetate} \end{gathered}$$
• Acetic acid reacts with Sodium bicarbonate to produce brisk effervescence due to the formation of ${\mathrm{CO}}_2$ gas, which causes lime water to turn milky.
• Therefore, the gas evolved is ${\mathbf{CO}}_{\mathbf{2}}$.
• The above-mentioned ${\mathrm{CO}}_2$ the gas reacts with Calcium hydroxide to form Calcium carbonate, which is insoluble in water.$$\begin{gathered} \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)\to {\mathrm{CaCO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Calcium}\mathrm{Calcium} \\ \mathrm{Hydroxide}\mathrm{carbonate} \end{gathered}$$
• Thus, the most effective method for testing for ${\mathrm{CO}}_2$ is to pass the gas through "limewater," which is a diluted solution of Calcium hydroxide (slaked lime).