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In complete combustion of hydrocarbons the colour of the flame is blue. But what is the reason behind the flame being blue and not green or black or any other colour?

Edit: I've searched the web for an answer to my question but all of them just equate blue flame to complete combustion and yellow to incomplete combustion. A similar or rather the same question has been asked here on chemistry stack exchange by a user but it just has one relevant answer. The motive behind asking this question again is to get a few more answers or in other words a few more second opinions so as to get a more balanced and clearer understanding of the matter.

Pumpkin_Star
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  • @M.Farooq Not exactly. There are three answers in all. Two of them don't answer the question and the third one isn't that easy to comprehend. – Pumpkin_Star Nov 02 '21 at 14:27
  • @Obina, You can edit/expand your question about what is not clear and show your search effort. Did you search the web? – AChem Nov 02 '21 at 14:28
  • The answer by Frazky is indeed the answer. The above two are not relevant. – AChem Nov 02 '21 at 14:29
  • @M.Farooq I have edited the question. Is it clearer now? – Pumpkin_Star Nov 02 '21 at 15:37
  • Unfortunately, it is closed now. The basic reason for blue flame is that hydrocarbons decompose to smaller simple diatomic molecules like $\ce{C2}$. By the intense heat of oxidations, these molecules are electronically excited. The excited molecules emit blue color. – AChem Nov 02 '21 at 15:40
  • @M.Farooq Any particular reason why the excited molecules emit blue colour? – Pumpkin_Star Nov 02 '21 at 16:07
  • It depends on the energy level difference between the ground state and excited state. Blue means that there is a big energy gap. – AChem Nov 02 '21 at 17:06
  • @M.Farooq Does this mean that if I somehow manage to adjust the energy difference, I can get green fire? – Pumpkin_Star Nov 02 '21 at 17:34
  • Yes, but molecular energy level in a flame is not in your hand. You can have green colored flame by introducing copper salt in flame. In fact, a lot of colors are possible. – AChem Nov 02 '21 at 18:48

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