Chapter 4, Problem 1DE

Interpretation Introduction

To determine: The facts related to chemical properties of the given salts to distinguish them.

Answer to Problem 1DE

Solution: The chemical properties of the given salts are enough to distinguish them.

Explanation of Solution

Given The three salts are named as sodium sulfide, sodium bicarbonate and sodium chloride.

The carbonate salts can be easily distinguished from any other salt by a basic carbonate test. In the test, salt is treated with dilute HCl and release of bubbles of ${\text{CO}}_{\text{2}}$ gas confirms the presence of carbonate. Due to the absence of carbonate in sodium chloride sodium sulfide it does not show any bubble formation on reaction with HCl.

Thus, sodium carbonate can be distinguished from sodium sulfide and sodium chloride by showing the following reaction:

  ${\text{NaHCO}}_{\text{3}}+\text{HCl}\to {\text{NaCl+H}}_{\text{2}}{\text{O+CO}}_{\text{2}}\uparrow$

Sodium chloride salt on reaction with silver nitrate forms sodium nitrate and silver chloride. Here, silver chloride so formed is insoluble in water thus, forms a white curd like solution. The reaction is as follows:

  $\text{NaCl}+{\text{AgNO}}_3\to {\text{NaNO}}_{\text{3}}+\text{AgCl}\downarrow$

Due to the absence of chlorine in sodium bicarbonate and sodium sulfide, they do not show the above reaction.

Now, sodium sulfide when exposed to moist air, it forms hydrogen sulfide gas that smells like rotten eggs. The chemical reaction is as follows:

  ${\text{Na}}_{\text{2}}^{}{\text{S+2H}}_{\text{2}}\text{O}\to 2\text{NaOH}+{\text{H}}_{\text{2}}\text{S}\uparrow$

The above reaction is not shown by ${\text{NaHCO}}_{\text{3}}$ and $\text{NaCl}$ . Thus, the above tests can distinguish sodium chloride, sodium bicarbonate and sodium sulfide.

Conclusion

Thus, the presence of sodium sulfide is confirmed by the evolution of hydrogen sulfide gas, the sodium bicarbonate is confirmed by the effervescence of carbon dioxide gas and sodium chloride is confirmed by the precipitate of silver chloride.