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Flame Test

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Title:
Flame Test

Aim:
To determine the cation in each of the unknown substance X, Y and Z by observing the flame colour of different metal compounds.

Introduction:
A distinctive feature of many s-block metals is their ability to produce flame colours.
At temperature of a Bunsen flame, a compound will decompose to give gaseous atoms of its constituent elements. When an electron in the gaseous atom absorbs energy from the flame, it will move from an orbital with lower energy to an orbital with higher energy. When such an electron returns from an orbital of higher energy to an orbital of lower energy, a photon with energy equal to the difference in energy of the two orbitals will be emitted. An emission line …show more content…

2. A spatula of sample (e.g. barium chloride) was put onto a clean watch glass. 3. The platinum wire is dipped into concentrated hydrochloric acid and then the crushed sample of salt to be tested. 4. The end of the platinum wire is heated strongly in a non-luminous flame again. 5. The colour of the flame at the wire is observed and recorded. 6. The platinum wire is cleaned thoroughly after testing each solid. The test is repeated with chloride of Ca2+, Cu2+, Mg2+, K+, Na+ and unknown solid X, Y and Z in turn.

Results: Compound | Colour of the flame | Cation Presents | Barium chloride | Apple green | | Calcium chloride | Brick red | | Copper(II) chloride | Bluish green | | Magnesium chloride | White | | Potassium chloride | Lilac | | Sodium chloride | Golden yellow | | X | Lilac | K+ | Y | Bluish green | Cu2+ | Z | Golden yellow | Na+ |

Discussion: 1. Why do certain metal ions give flame colours in this way?
The elements have their outer electrons loosely bound so that they can be easily excited to higher energy levels on heating. As these electrons return to their ground states, radiations are emitted. It happens that for many Group I and II metals, these emitted radiations fall into the visible range of the spectrum, so that they can be seen by eyes, i.e., visible. 2. What is the

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