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Topic: Flame Test LAB  (Read 6107 times)

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MulherLouca

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Flame Test LAB
« on: May 11, 2005, 03:41:51 PM »
Hi everyone!

I'm a little stuck on this one as i did not had enough time to analyse my experiments in class.  

i've tryed to figure out the relation between an element and the color of flame produced by i'm really confused.

So my question is How can i determine an unknown element when i know it's color of the flame?

1 of the 2 question i have to  answer is : "what chemical would you use if you were making a green flare"?

Can anyone explain me the concept behind this?


Garneck

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Re:Flame Test LAB
« Reply #1 on: May 11, 2005, 03:49:29 PM »
Hi everyone!

I'm a little stuck on this one as i did not had enough time to analyse my experiments in class.  

i've tryed to figure out the relation between an element and the color of flame produced by i'm really confused.

So my question is How can i determine an unknown element when i know it's color of the flame?

1 of the 2 question i have to  answer is : "what chemical would you use if you were making a green flare"?

Can anyone explain me the concept behind this?



Green flame? You'd need a barium or copper salt.

As far as I remeber, ammonia also gives a green flame while burning.

Offline constant thinker

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Re:Flame Test LAB
« Reply #2 on: May 11, 2005, 08:10:00 PM »
Photons are emitted by electrons "jumping" in energy. When they're excited they go up a level. When they drop back they have to get rid of the energy. The energy is released as a photon and its wave length determines color. Correct if I'm wrong or add more if I missed something. Hope I helped a little.
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Offline jdurg

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Re:Flame Test LAB
« Reply #3 on: May 11, 2005, 08:22:47 PM »
No, that was a good explanation.   ;D  The reason why each element has its own particular color is due to their electronic configuration.  Even if the elements are isoelectronic, the different nuclear sized causes the amount of energy associated with the transition to be a little bit different.  (Hence why calcium and potassium emit different colors in a flame).  So these electrons in the ions absorb energy from the flame which causes them to 'jump up' to a different energy level.  (Since the excess energy forces them further from the nucleus).  As soon as that initiating energy is removed (ion moves away from the energy source), the ion gets rid of that excess energy and the electron moves back to the ground state.  When it goes back down to that ground state, a specific wavelength is given off which we see as a color.  A similar process occurs in high voltage gas discharge tubes.

For the green color, barium salts are typically used.  Copper isn't all that great of a color donor in terms of green.  Cu tends to give off a bluish color more often than not.  Ammonia emits no color when placed in a flame.
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Re:Flame Test LAB
« Reply #4 on: May 11, 2005, 08:36:37 PM »
I figured it had to do with electron configuration, but wasn't 100% on it.
When I was younger my dad used to put some copper tubing in a sleeve of what seamed a combination of some plastic and metal tubing and he'd thow it in a fire. It was really cool since the flame started green then went to purple and was different colors. That is one thing that got me intrested in chemistry, but sadly I was denied to go into chemistry one as a sophmore. If it wasn't for the stupid teacher.
"The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.' " -Ronald Reagan

"I'm for anything that gets you through the night, be it prayer, tranquilizers, or a bottle of Jack Daniels." -Frank Sinatra

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