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Chemical Tests spec points 2.44 to 2.49 - Coggle Diagram
Chemical Tests
spec points 2.44 to 2.49
FLAME TESTS
(cations)
Li+ = red
Na+ = yellow
K+ = lilac
Ca2 + = orngae/red
Cu2+ = blue/green
METHOD:
Get nichrome wire and dip nichrome wire into HCL and into the bunson burner to clean it. Put the wire into the HCL and compound then into the fire to see its colour
spec points =.
2.45
describe how to carry a flame test -----------------------------------------------------------------------
2.46
know the colours formed in flame tests for these cations: Li+ is red, Na+ is yellow, K+ is lilac, Ca2+ is orange-red, Cu2+ is blue-green
GAS TESTS
Hydrogen (H2)
= light a splint put in the the hydrogen gas and it should make a squeaky pop.
Oxygen (O2)
= light a splint and blow it out so its glowing and when it goes into the oxygen gas and it should relight
Carbon Dioxide (CO2)
= add CO2 into lime water and it will turn cloudy
Ammonia (NH4)
= add damp red litmus paper in ammonia gas and it should turn the paper blue (dangerous gas given off so don't inhale it)
chlorine (Cl2)
= put universal indicator paper in chlorine gas and it should turn red then bleach white (dangerous gas given off so don't inhale it)
spec point =
2.44
describe tests for these gases: hydrogen, oxygen, carbon dioxide, ammonia, chlorine
relevance = can help detect safety issues with products
MORE CATION TESTS
Testing With Sodium Hydroxide
METHOD:
add a few drop sof sodium hydroxide (NaOH) to the ion and watch the precipitate form
Al3+ = forms a white precipitate
Ca2+ = forms a white precipitate
Mg2+ = forms a white precipitate
Cu2+ = forms a blue precipitate
Fe2+ = forms a green precipitate
Fe3+ = forms a brown precipitate
Testing for Ammonium Cations
METHOD:
Add sodium hydroxide into a boiling tube. Heat the mixture gently and test the gas given off with litmus paper.
ammonium NH4 + = turns from damp red litmus paper to blue paper
spec point =
2.47
describe tests for these cations: NH4+ using sodium hydroxide solution and identifying the gas evolved, Cu2+, Fe2+ and Fe3+ using sodium hydroxide solution.
relevance: helps identify positive ions
Water Test
Blue hydrated copper sulfate urns into white anhydrous copper sulfate when heated. The reaction is reversible so we can test that if it goes blue again, water is present
the colour change would be white --> blue and this can be reversed
Balanced Equation
CuSo4.5H2O(s) → CuSO4 (s) + 5H2O (l)
spec point =
2.49
describe a test for the presence of water using anhydrous copper(II) sulfate
PURE WATER TEST
to test if water is pure or not test if the boiling point is exactly 100°C and the freezing point is exactly 0°C
relevance = determines if water is pure/safe to consume
ANION TESTS
spec point =
2.48
describe tests for these anions: Cl –, Br – and I – using acidified silver nitrate solution , SO4 2– using acidified barium chloride solution • CO3 2– using hydrochloric acid and identifying the gas evolved.
METHOD:
add dilute nitric acid then add silver nitrate
Cl - = forms a white precipitate
Br - = forms a cream precipitate
I - = forms a yellow precipitate
Testing for Carbonate Ions
METHOD:
add a few drops of dilute HCL into the ion and a colourless gas will be given off
carbonate CO3 2– = the limewater turns cloudy
Testing for Sulfate Anions
METHOD:
add a few drops of barium chloride solution into the ion
sulphate SO4 2– = a white precipitate forms
relevance: helps identify negative ions