Tests For Anions And Cations (2) Flashcards
To find Cations you can use _________ tests
Flame
Lithium burns with a ______ flame
Red
Sodium burns with a _________-_________ flame
Yellow-orange
Potassium burns with a _________ flame
Lilac
Calcium burns with a ________ _____ flame
Brick red
To do a flame test you need to clean the wire by dipping it in some dilute __________________ ______ and holding it in a flame. Then when it shows no ___________, it is clean and you can dip it into the sample (E.g Lithium) and it will show a colour
Hydrochloric acid
Colour
Some metals form a coloured precipitate with ________
NaOH
Sodium Hydroxide
Many metal hydroxides are insoluble and precipitate out of solution when formed. Some of these hydroxides have a characteristic colour. So in this test you add a few drops of ___________ _______________ solution to the solution of your unknown compound - in the hope of forming an insoluble _____________. If you get a colour then you can tell which metal was in the compound
Sodium hydroxide
Insoluble hydroxide
If the colour of the precipitate is blue then what is the metal ion
Copper (||)
If the colour of the precipitate is sludgy green then what is the metal ion
Iron (||) 2
If the colour of the precipitate is reddish brown then what is the metal ion
Iron (|||) 3
Equation/ionic reaction of cu2+ and NaOH
Cu2+ (aq) + 2OH- (aq) → Cu(OH)2 (s)
Equation/ionic reaction of Fe2+ and NaOH
Fe2+ (aq)+ 2OH- (aq) → Fe(OH)2 (s)
Equation/ionic reaction of Fe3+ and NaOH
Fe3+ (aq) + 3OH- (aq) → Fe(OH)3 (s)
An _____________ compound + NaOH gives off Ammonia which does not smell good
Ammonium
How to test for ammonia gas
By using a damp piece of red litmus paper that will turn blue if ammonia is present
Add some sodium hydroxide to your mystery substance in a test tube If there’s ammonia given off this means there are ______________ ions in your mystery substance.
Ammonium
Hydrochloric acid can help detect ____________ which are anions
Carbonates
To test for carbonates, add dilute hydrochloric acid (HCl) to your test sample. If carbonates are present then __________ __________ will be released
Carbon dioxide
Test for carbon dioxide:
Limewater will go milky
How do you test for sulfates? What appears to show that the original compound was a sulfate
Hydrochloric acid followed by barium chloride
White precipitate
Why is hydrochloric acid added to the ‘test for sulfates’ experiment
To clean out any carbonate or sulfite ions
To test for halides (chloride, bromide or iodide ions,) add dilute __________ acid, followed by ____________ ____________ solution
Nitric
Silver nitrate solution
What do you use to test for chloride ions and what will be formed? A chloride ion gives a __________ precipitate of silver chloride
Nitric acid followed by silver nitrate solution
White
What do you use to test for bromide ions and what will be formed? A bromide ion gives a __________ precipitate of silver bromide
Nitric acid followed by silver nitrate solution
Cream
What do you use to test for iodide ions and what will be formed? An iodide ion gives a ___________ precipitate of silver iodide
Nitric acid followed by silver nitrate solution
Yellow
Why is nitric acid added to the ‘test for halides’ experiment
To clean out any carbonates or sulfite ions
What are flame tests used to identify
Metal ions (Lithium, sodium, potassium, calcium)
What is sodium hydroxide used to identify
Metal ions (Copper and iron)
How can you use NaOH to test for ammonia
After adding the NaOH, check to see if it turns damp red litmus paper blue
What is hydrochloric acid used to test for
Carbonates
What is HCI and Barium chloride used to test for
Sulfates
What can you test for by adding dilute nitric acid followed by silver nitrate solutions (AgNO3)
Halides
How to test for Lithium, sodium, potassium, calcium
Flame tests
How to test for Copper and iron
Add sodium hydroxide (NaOH) and see the colour of precipitate
How to test for ammonia
Add sodium hydroxide (NaOH) and then see if it turns damp red litmus paper blue
How to test for carbonates
Add dilute hydrochloric acid to your test sample
How to test for sulfates
Dilute HCI followed by barium chloride solution
How to test for halides
Nitric acid (HNO3) followed by silver nitrate solution
Hydrochloric acid and nitric acid are both used to clean out any traces of carbonates or sulfite ions - which is used for which experiment?
Hydrochloric acid is used to test for sulfates
Nitric acid is used to test for halides