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flame test lab

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Introduction

Aim The aim of the experiment is to give a qualitative introduction to the spectra emitted by some s-block elements when their atoms are excited by heating samples in a Bunsen flame. Theory "The energy levels in atoms and ions are the key to the production and detection of light. Energy levels or "shells"exist for electrons in atoms and molecules. The colors of dyes and other compounds results from electron jumps between these shells or levels. The colors of fireworks result from jumps of electrons from one shell to another. Observations of light emitted by the elements is also evidence for the existence of shells, subshsells and energy levels. The kinds of light that interact with atoms indicate the energy differences between shells and energy levels in the quantum theory model of the atom. Typically the valence electrons are the ones involved in these jumps. Atoms have two kinds of states; a ground state and an excited state. The ground state is the state in which the electrons in the atom are in their lowest energy levels possible (atoms naturally are in the ground state). This means the electrons have the lowest possible values for "n" the principal quantum number. Specific quantized amounts of energy are needed to excite an electron in an atom and produce an excited state. ...read more.

Middle

Wear your googles, gloves and gown before start working 2. Swich on the lamp and look at the bulb through the hand spectroscope. Look for a series of colours, one running into the next. This is the continuous spectrum. 3. Hold the spectroscope up to a window which does not face the sun. This could result in permament damage to your eyes. You should see the continuous spectrum of visible light. 4. Make sure your flame test wire is clean. 5. Prepare needed substances. 6. Light the Bunsen burner. 7. Dip the flame test wire into the hydrochloric acid and next take some strontium chloride on it and put it into Bunsen fire. Watch the colour of the flame. Your partner should be watching the flame through the hand spectroscope. Look for the brightly coloured lines. There are several lines for each element and it will be propably not possible to get them all into view at once. 8. Dip the flame test wire again into the hydrochloric acid to clean it from the substance. 9. Repeat steps 4-8 with calcium chloride (CaCl2), sodium chloride (NaCl), potassium chloride (KCl), CuSO4 x 5H2O and lithium chloride (LiCl) Safety guidelines !!! - Work areas should be arranged so that a person does not need to travel through a high-hazard area while attempting to exit the laboratory during an emergency. ...read more.

Conclusion

- 405 nm, 450 nm, 480 nm, green - 550 nm, red - 650 nm), more than 12 lines for calcium chloride (blue - 420 nm, 430 nm, 450 nm, 480 nm, 500 nm, 520 nm, green - 540nm, 570nm, yellow - 600 nm, orange - 630 nm, red - 675 nm, 680 nm), one line for sodium chloride (yellow - 600 nm), 6 lines for CuSO4 x 5H2O (blue - 455 nm, 510 nm, green - 520 nm, 530 nm, 575 nm and yellow - 590 nm) and 7 lines for potassium chloride (blue - 450 nm, 465 nm, 480 nm, 485 nm, 505 nm, green - 535 nm and yellow - 590 nm). The results of the experiment weren't the same. It might be because of the fact we saw also the spectrum of electric lamps which were switched on and the shadows of other people working at the labolatory. Ways of improving the results: - less shadows of other people - more concentration during the experiment - use of more modern equipment - looking throug the spectroscope in the dark room in order to avoid seeing the electric lamp's light spectrum - the experiment should be repeated to get some more reliable results Sources - "Chemistry for the IB Diploma (standard and higher level)" by Geoff Neuss - "Chemistry" (second edition) by John Green and Sandru Damji - http://webmineral.com/help/FlameTest.shtml - http://en.wikipedia.org/wiki/Flame_test - http://www.800mainstreet.com/spect/emission-flame-exp.html ...read more.

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