Flame test

Flame test

Description:  Small amounts of different salts are burned in the flame of a Bunsen burner.  Sodium burns orange, potassium - purple/blue, barium - green, and lithium – red

Concept:   When an element is burned, the electrons will be excited.  Then as these electrons fall back from one energy level to another, they will emit photons of light.  These photons will have different colors depending on the element and its discrete energy levels.  That is, different wavelengths of light (colors) will be emitted when the electrons of  different elements go down the step(s) between their energy level(s).  Each element will have its own set of steps, therefore each will have its own color.

 

Procedure: 

            Dip the wire loop of a glass rod into the water/con.HCI

            Use this wet loop to pick up some salt.

            Hold the salt in the flame and burn to show color.

            Do the same for all salts, being sure to use a different glass rod-with-wire loop

for each salt.  Also be careful not to drop any salt onto the Bunsen burner.

Clean-up:  Be sure to turn the gas off if you use a Bunsen burner.  In rm. 122 you will need to have Alice open the cupboard to get to the gas valve.  Wash wire loops well to

ensure all salt is removed.  Clean off any salt that might have dropped onto the Bunsen burner or propane torch.

Flame Test Colors

Li⁺                                        Deep red (crimson)

Na⁺                                       Yellow

K⁺                                         Violet

Ca²⁺                                      Orange-red

Sr²⁺                                      Red

Ba²⁺                                      Green

Cu²⁺                                     Blue-green

Cu¹⁺                                     Green

Cu²⁺                                     Blue

Fe                                         Yellow to red-orange (depending on anion and charge of Fe); in
                                               rare cases, can form complex ion with a deep blue color

Fe²⁺                                      yellow-green (depending on the anion)

Fe³⁺                                      orange-red (depending on the anion)

Co²⁺                                     Pink      

Cr³⁺                                      Violet  to Green

Ni²⁺                                      Green

Mn²⁺                                    Pink

Pb³⁺                                      blue-green (Pb²⁺ and Pb⁴⁺ are colorless)

V²⁺                                       violet

V³⁺                                       blue-green

MnO₄^-                                  Purple (Mn w/ +7 oxidation state is purple)

CrO₄^2-                                  Yellow

Cr₂O₇^2-                                Orange

Cu(NH₃)₄²⁺                         Dark Blue; produced when ammonia is added to Cu²⁺ solutions

FeSCN²⁺                              Red-brown, Wine-red to dark orange

CoCl₄^2-                                Blue (Co²⁺ with HCl will form a CoCl₄^2- complex that is blue)

Ti(H₂O)₆³⁺                           Purple

 

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