Flame Test
Discussion Questions 1. Why do different metals have different characteristic flame test colours?
The photons emitted during the test precisely match the quantum energy difference between the excited state and the ground state. For different elements the spacing between the ground state and the higher energy levels is different. So different elements have different flame test colours. 2. Most salts contain a metal and a non-metal. Look at the compounds we tested and determine whether it is the metal or the non-metal that is responsible for the colour produced in the flame test for that salt. How can you be sure your answer is correct?
Metal is responsible for the colour produced in the flame test for that salt. All salts contain chloride ion. If non-metal ion, chloride, is responsible for the colour, all colour produced will be the same.
3. Why do the chemicals have to be heated in the flame before the coloured light is emitted?
For the coloured light to be emitted, the electrons have to get enough energy to jump higher away from the nucleus and then fall back closer to it. When chemicals are heated, the flame provides energy for the electrons.
4. Could flame tests be useful in determining identities of metals in a mixture of two or more salts? If so, what problems might arise? If not, why not? Explain your answer.
In determining identities of metals in a mixture of two or more salts, flame tests will not be useful. There will be mixture of colour produced in the flame test and we won’t be able to determine which one of the mixture is responsible for which colour. 5. Which method is better for precisely identifying elements: examining the full spectrum using a spectroscope or using a flame test? Use your experience in the lab with both of these methods in answering this question. Justify your answer.
Flame tests are unreliable and we can make quantitative measurements with spectroscope that we can't with a flame test. Some elements give
The photons emitted during the test precisely match the quantum energy difference between the excited state and the ground state. For different elements the spacing between the ground state and the higher energy levels is different. So different elements have different flame test colours. 2. Most salts contain a metal and a non-metal. Look at the compounds we tested and determine whether it is the metal or the non-metal that is responsible for the colour produced in the flame test for that salt. How can you be sure your answer is correct?
Metal is responsible for the colour produced in the flame test for that salt. All salts contain chloride ion. If non-metal ion, chloride, is responsible for the colour, all colour produced will be the same.
3. Why do the chemicals have to be heated in the flame before the coloured light is emitted?
For the coloured light to be emitted, the electrons have to get enough energy to jump higher away from the nucleus and then fall back closer to it. When chemicals are heated, the flame provides energy for the electrons.
4. Could flame tests be useful in determining identities of metals in a mixture of two or more salts? If so, what problems might arise? If not, why not? Explain your answer.
In determining identities of metals in a mixture of two or more salts, flame tests will not be useful. There will be mixture of colour produced in the flame test and we won’t be able to determine which one of the mixture is responsible for which colour. 5. Which method is better for precisely identifying elements: examining the full spectrum using a spectroscope or using a flame test? Use your experience in the lab with both of these methods in answering this question. Justify your answer.
Flame tests are unreliable and we can make quantitative measurements with spectroscope that we can't with a flame test. Some elements give