tests Flashcards
What is the test for Lithium, Sodium, Potassium and Calcium?
these are cations/positive ions
- make a solution of the metal compound.
- put a bunsen burner on a blue flame.
- Clean a piece of nichrome wire by dipping it in acid and then place it into the flame until no colour is seen.
- Dip the clean nichrome wire into the metal compound solution and place it in the flame.
observe the colour change.
What colour does Potassium go in the flame test?
Lilac
What colour does Lithium go in the flame test?
Scarlet/Crimson
What colour does calcium go in the flame test?
Brick Red
What colour does Sodium go in the flame test?
yellow
What is the test for Ammonium?
- Start with a solution of the compound.
- add sodium hydroxide
- warm it gently
- test any gas that is made with damp red litmus paper
- If the damp red litmus paper goes blue then the gas was ammonia and therefore ammonium ions are present.
What is the test for Coppper(II), Iron (II) and Iron (III)
hydroxide ions
- Place a small amount of the metal solution in a test tube.
- Add a small amount of sodium hydroxide.
- Observe the colour of the precipitate.
What colour does Copper (II) precipitate go?
Blue
What colour does Iron (II) precipitate go?
green
What colour does Iron (III) precipitate go?
orangey brown
What is the test for the halides?
- Add nitric acid to check it is not a carbonate.
2. Add silver nitrate and observe the colour of the precipitate
What colour does Chlorine go in the halide test?
white
What colour does bromine go in the halide test?
cream
what colour does iodine go in the halide test?
yellow
What is the test for sulphate ions?
Test: Add hydrochloric acid to check it is not a carbonate.
Add a few drops of Barium chloride solution
Result: White precipitate (Barium sulphate)
What is the test for carbonate ions?
Add an acid e.g. nitric, hydrochloric acid
If you see bubbles carbonate ions are present.
The bubbles are carbon dioxide so can be tested with limewater (the limewater will go milky)
What is the test for hydrogen?
A lit splint in the suspected gas.
Result: Goes out with a squeaky pop
What is the test for oxygen?
A glowing splint in the suspected gas
Result: the splint relights
What is the test for Carbon Dioxide?
Add limewater to the suspected gas
Result: limewater goes milky
What is the test for Ammonia?
Dip red litmus paper in suspected gas.
Result: goes blue (alkali)
What is the test for chlorine?
Dip damp blue litmus paper in suspected gas.
Result: goes red then white (acidic gas)
Why does the limewater go milky when you add CO2
the carbon dioxide reacts with the calcium hydroxide forming calcium carbonate and water
What is the chemical test for water
White anhydrous copper (II) sulphate turns blue
What type of reaction is the chemical test for water?
reversible and exothermic
What is the physical test for water?
Pure water freezes at 0 degrees and boils at 100 degrees
Why does the ‘hydroxide’ test work?
Most metal hydroxides are insoluble (not Group 1 metals though)
Why does the test for sulphate ions work?
Barium sulphate is insoluble
