Flame tests (1 Viewer)

[zariarnakh]

there is me and one other person in my class doing independent study for this elective, and the flame test prac. is giving us some trouble. if anyone could give us some info. that would be great because we can't seem to find anything.

 

[brenton1987]

Is this the dot point youre talking about?
"Perform first-hand investigations to observe the flame colour of Na⁺, K⁺, Ca²⁺, Ba²⁺, Sr²⁺ and Cu²⁺."

When the ions are aspirated into the flame the elctrons absorb energy and get promoted to higher energy levels. When the electrons release the energy they fall back to the ground state. The energy is released as electromagnetic radiation of specific frequencies. Each individual element has a unique emission spectrum by which it can be identified and measured (Atomic Absorption Spectroscopy).

So each of the ions above will produce their own colour when aspirated into a flame.
Na⁺ - Yellow
K⁺ - Lilac
Ca²⁺ - Red-orange
Ba²⁺ - Light Green
Sr²⁺ - Crimson
Cu²⁺ - Green/Blue-green depending on the presence of a halide anion.

 

[zariarnakh]

that's exactly it.
thank you so much for your help
i wish i got more of it from school.

 

[MrZ]

This practical would require you to use a spectrometer of sorts so you can actually see the emission spectra produced by the excited ions and get quantifiable data (seeing and determining the various wavelengths of the visible emission spectra lines). The alternative is simply observing the flame colours of each metal ion giving qualitative data. There is a subtle difference depending on what you want to observe. The other favourite HSC question is related to this practical is a 'risk assessment'. Mr Z.