Chapter U4.85, Problem 7E

Interpretation Introduction

Interpretation: The reason for the aqueous solution of washing soda, ${\text{Na}}_2{\text{CO}}_3$ to be basic in nature needs to be determined.

Concept Introduction: An Arrhenius base is a substance that ionizes in water to generate hydroxide ion, ${\text{OH}}^{-}$ . An aqueous solution of ${\text{Na}}_2{\text{CO}}_3$ is basic in nature because it produces ${\text{OH}}^{-}$ ions in the solution.

Answer to Problem 7E

The aqueous solution of ${\text{Na}}_2{\text{CO}}_3$ is basic since ${\text{Na}}_2{\text{CO}}_3$ hydrolyzes in water, producing ${\text{OH}}^{-}$ ions.

Explanation of Solution

Sodium carbonate ${\text{Na}}_2{\text{CO}}_3$ hydrolyzes in water producing sodium hydroxide, $\text{NaOH}$ and carbonic acid, ${\text{H}}_2{\text{CO}}_3$ . $\text{NaOH}$ is a strong base and ionizes completely in water to give ${\text{OH}}^{-}$ ions. The generated ${\text{OH}}^{-}$ ions make the solution basic.

  $\begin{array}{l}{\text{Na}}_2{\text{CO}}_3\left(\text{aq}\right)+{\text{2 H}}_2\text{O}\left(\text{l}\right)\to 2\text{ NaOH}\left(\text{aq}\right)+{\text{H}}_2{\text{CO}}_3\left(\text{aq}\right)\\ \text{NaOH}\left(\text{aq}\right)\to {\text{Na}}^{+}\left(\text{aq}\right)+{\text{OH}}^{-}\left(\text{aq}\right)\end{array}$

Conclusion

The aqueous solution of washing soda is basic due to the generation of ${\text{OH}}^{-}$ ions in solution.