Qualitative Analysis of Inorganic Chemistry - Grade 12

Qualitative analysis is used to identify compounds. Those compounds are made of cations and anions. These compounds can be in a single mixture. Therefore we have to follow a specified procedure to identify these compounds one by one. There are many different experiments to identify different compounds. In qualitative analysis, we observe a physical change, when a reaction is being occurred or after completed the reaction.

Physical changes can be seen in a reaction

  • forming a colourful solution
  • forming a precipitate
  • emitting a gas or gases

Cations and Anions

In the qualitative analysis of inorganic chemistry in grade 12, we have some cations (positively charged ions) to identify such as Cu2+, Fe2+ and more.

As cations, there are few anions we have to learn in qualitative analysis in inorganic chemistry section.


Example to Qualitative Analysis

Now we are going to see a small example which explains what is qualitative analysis and how it is done to identify cations and anions.


Identify ferric chloride and ferric sulfate ( FeCl3 and Fe2(SO4)3)

Questions

There are two brown colour solutions in two bottles. You have to identify these two solutions by doing some experiments. But you have informed that, these solutions contain ferric chloride (FeCl3) and ferric sulfate (Fe2(SO4)3). So you have to decide which bottle contains which compound.


Answer

  • Ferric +3 cation is common for both FeCl3 and Fe2(SO4)3 compounds.
  • So we have to know, we are going to test anions. (chloride and sulfate).
  • Add BaCl2 solution to both brown solution.
  • In one solution, there is no difference after addition of BaCl2.
  • In other solution, a white precipitate is given.
  • When we consider possible reactions, it's clear that BaSO4 is the only precipitate which is deposited easily at bottom of the solution. That solution had the Fe2(SO4)3.


Qualitative Analysis for cations



Qualitative Analysis for anions



Qualitative Analysis for gases

Problems