Chapter 22, Problem 47E

Interpretation Introduction

Interpretation:

A chemical test needs to be determined whether a white solid salt is ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$ or ${\text{Na}}_{\text{2}}{\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$ with chemical equations.

Concept introduction:

When ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$ is warmed with dilute HCl, no visible reaction takes place.

When ${\text{Na}}_{\text{2}}{\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$ is warmed with dilute HCl, the solution turned slightly cloudy as yellow sulfur is formed. The solution becomes denser when warm.

When ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$ is add to silver nitrate solution no reaction at first, then a faint white precipitate appeared due to the formation of silver sulfate $\left({\text{Ag}}_{\text{2}}{\text{SO}}_{\text{4}}\right)$.

A white precipitate is obtained when ${\text{Na}}_{\text{2}}{\text{S}}_2{\text{O}}_3$ is add to silver nitrate solution. The precipitate is dissolved on shaking. When more ${\text{AgNO}}_{\text{3}}$ is added, the remaining precipitate turns yellow.