Write the following experiments in the lab manual. Identification of cations by adding ammonium hydroxide solution to the aqueous solutions of Ca+2, Cu+2, Fe+2, Fe+3 , Pb+2 and Zn+2 .
Answers
Answer:
Our Objective
Our objective is to determine the cation present in a given salt.
The Theory
What is Qualitative Analysis?
Qualitative analysis is a method of Analytical chemistry that deals with the determination of elemental composition of inorganic salts. It is mainly concerned with the detection of ions in an aqueous solution of the salt.
The common procedure for testing any unknown sample is to make its solution and test this solution with various reagents for the ions present in it. Testing with various reagents gives characteristic reaction of certain ions, which may be a colour change, a solid formation or any other visible changes. There are separate procedures for detecting cations and anions, called the Cation Analysis and Anion Analysis.
Let us discuss about the Qualitative Analysis of Cations.
Qualitative Analysis of Cations
Preliminary Tests
Some preliminary tests needs to be done before doing the analysis of cations.
(a) Physical Appearance: Colour and Smell
The physical examination of the unknown salt involves the study of colour, smell and density. The test is not much reliable, but certainly helpful in identifying some coloured cations. Characteristic smell helps to identify some ions like ammonium ion.
(b) Charcoal Cavity Test
This test is based on the fact that metallic carbonates when heated in a charcoal cavity decomposes to give corresponding oxides. The oxides appear as coloured incrustation or residue in the cavity. In certain cases, the oxides formed partially undergo reduction to the metallic state producing metallic beads or scales.
Examples: