English for Chemists
How is the test performed?
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English-for-Chemists АНГЛИЙСКИЙ
How is the test performed?
First, you need a clean wire loop. Platinum or nickel-chromium loops are most common. They may be cleaned by dipping in hydrochloric or nitric acid, followed by rinsing with _____________ (distill) or _____________ (deionise) water. Test the _______________ (clean) of the loop by 65 inserting it into a bunsen burner flame. If a burst of color is produced, the loop was not _____________ (sufficient) clean. Ideally, a separate loop is used for each sample to be tested, but a loop may be _____________ (careful) cleaned between tests. The clean loop is dipped in either a powder or solution of an ionic salt. The loop with sample is placed in the clear or blue part of the flame and the resulting colour is observed. What are the limitations of this test? The value of the flame test is limited by interference from other brighter colours and by ambiguities where certain different metals cause the same flame colour. Sodium, in particular, is present in most compounds and will colour the flame. Sometimes a coloured glass is used to filter out light from one metal. Cobalt glass is often used to filter out the yellow of sodium. 4. What is the singular of the word ‘spectra’? 5. Some of the sentences in the article are passive. Turn them into active. Flame Test Colours 6. Fill the names of the chemical elements into the following chart. Symbol Element Color As Blue B Bright green Ba Pale/Yellowish Green Ca Orange to red Cs Blue Fe Gold In Blue K Lilac to red Li Magenta to carmine 66 Mg Bright white Mo Yellowish green Na Intense yellow P Pale bluish green Pb Blue Rb Red to purple-red Sb Pale green Se Azure blue Sr Crimson Te Pale green Tl Pure green Zn Bluish green to whitish green Adapted from: http://chemistry.about.com/library/weekly/aa110401a.htm http://chemistry.about.com/od/analyticalchemistry/a/flametest.htm Download 1.14 Mb. Do'stlaringiz bilan baham: |
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