Flame tests to identify metal ions Flashcards
What does Lithium burn with?
red flame
What does sodium burn with?
yellow flame
What does potassium burn with?
lilac flame
What does calcium burn with?
orange-red flame
What flame do Copper ions give?
blue-green flame
How do you do the flame test?
-you need a clean platinum wire loop by dipping it in some dilute HCL then holding it in a flame.
-once you hold the loop in the flame and it burns without any colour you can dip it into the sample you want to test
-then put it back in the clear part of the Bunsen flame (hottest part)
When do some metals form a coloured precipitate?
With NaOH
Are metal hydroxides insoluble or soluble?
Insoluble
What is the test for finding which metal was in a compound?
- add a few drops of sodium hydroxide solution to a solution of your mystery compound in a test tube
- if you get a coloured insoluble hydroxide you can then tell which metal was in the compound
What is the colour of precipitate with Copper (II) metal ion when added to NaOH?
blue
What is the colour precipitate with Iron (II) metal ion?
Sludgy green
What is the colour precipitate with Iron (III) metal ion when reacting with NaOH?
Reddish Brown
How can you test for ammonia gas? What is the colour change?
-damp piece of red litmus paper
-if there is ammonia present, the paper will turn blue
How can you test whether a substance contains ammonium ions?
-add some sodium hydroxide to a solution of your mystery substance in a test tube
- if there is ammonia given off this means there are ammonia ions in your mystery substance
How can you test for carbonates?
- add dilute hydrochloric acid to your test sample
-if carbonates are present then carbon dioxide will be released
What do carbonates give off?
give off carbon dioxide with HCL
What is the word equation for testing for carbonates?
carbonate + acid = carbon dioxide + water
What precipitate do sulfate ions produce?
produce a white precipitate
How do you test for a sulfate ion?
- add dilute HCL
- followed by barium chloride solution
What does the white precipitate of barium sulfate mean?
The original compound was a sulfate
Why is hydrochloric acid added?
- to get rid of any traces of carbonate or sulfate ions before you do the test
-they would both produce a precipitate which would crowd the result
How can you test for chloride, bromide, iodide ions?
- add dilute nitric acid followed by silver nitrate solution
What does a chloride ion give? What is this word equation?
-white precipitate of silver chloride
- Ag (aq) + + Cl-(aq) = AgCl(s)
What does a bromide ion give? What is this word equation?
-cream precipitate of silver bromide
- Ag+(aq) +Br(aq)- = AgBr(s)
What does a iodide ion give? What is this word equation?
-yellow precipitate of silver iodide
- Ag+(aq) +I(aq)- = AgI(s)
What is nitric acid used for?
- to get rid of carbonate or sulfite ions before the test
