Question

What would you observe on adding dilute hydrochloric acid to sodium bicarbonate placed in a test tube?

Answer 1

• When an acid reacts with metal carbonate or metal bicarbonate(Metal hydrogen carbonate) it forms salt of that metal along with water $\left({\mathrm{H}}_2\mathrm{O}\right)$ and carbon dioxide$\left({\mathrm{CO}}_2\right)$.

The reaction of dilute hydrochloric acid with sodium bicarbonate:

• Sodium bicarbonate $\left({\mathrm{NaHCO}}_3\right)$ reacts with dilute hydrochloric acid $\left(\mathrm{HCl}\right)$ to form sodium chloride $\left(\mathrm{NaCl}\right)$, carbon dioxide $\left({\mathrm{CO}}_2\right)$ , and water $\left({\mathrm{H}}_2\mathrm{O}\right)$.

Reaction involved:

• ${\mathrm{NaHCO}}_3\left(\mathrm{s}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to \mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)$
• The production of carbon dioxide $\left({\mathrm{CO}}_2\right)$ causes brisk effervescence (rapid production of gas).

Test for production of carbon dioxide:

• Carbon dioxide reacts with lime water $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ and forms a white precipitate of calcium carbonate $\left({\mathrm{CaCO}}_3\right)$ with water $\left({\mathrm{H}}_2\mathrm{O}\right)$, this reaction indicates the presence of carbon dioxide.
• ${\mathrm{CO}}_2\left(\mathrm{g}\right)+\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)\to {\mathrm{CaCO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$
• Therefore, we observe brisk effervescence on adding dilute hydrochloric acid to sodium bicarbonate.