(SC25) Qualitative analysis: Tests for ions Flashcards
Colour of lithium (Li+) flame test
red
Colour of sodium (Na+) flame test
yellow
Colour of potassium (K+) flame test
lilac
Colour of calcium (Ca2+) flame test
orange-red
Colour of copper (Cu2+) flame test
blue-green2
How does flame photometer work?
The flame photometer measures the light intensity of the flame colours produced by metal ions. Its data is used to determine the cpncentration of a metal ions in a dilute solution.
A flame photometry seperates colours and produces a spectrum of the light emitted by each metal ion. A metal ion in a unknown solution can be identified by matching its spectrum to the spectrum from a known spectrum ion.
Iron II (Fe2+) precipitation reaction
green
Iron III (Fe3+) precipitation reaction
brown
Copper (Cu2+) precipitation reaction
blue
Calcium (Ca2+) precipitation reaction
white
Aluminium (Al3+) precipitation reaction
white
Testing for carbonate ions
Add dilute hydrochloric acid to the test substance and look for bubbling caused by the production of carbon dioxide. Since the bubbles cold be due to a different gas, such as hydrogen, you should carry out a confirmatory test. If the bubbles do contain carbon dioxide, they turn limewater.
Testing for sulfate ions
Add a few drops of dilute hydrochloric acid. This acidifies the solution and removes carbonate ions that might also give a precipitate the test. Then add a feew drops of barium chloride solution. A white precipitate of barium sulfate forms if the sample contains sulfate ions.
Testinf for halide ions
Add a few drops of dilute nitric acid. This acidifies the solution and removes carbonate ions that might also give a precipitate in the test. The add a few drops of silver nitrate solution. Different colouted silver halide precipitates are formed.
