2.44: Describe the Tests for these Gases: Hydrogen, Oxygen, Carbon Dioxide, Ammonia and Chlorine

TEST FOR HYDROGEN:

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HYDROGEN TEST

Diagram showing the Test for Hydrogen

METHOD: Collect gas into a boiling tube Insert lit Splint inside the boiling tube

RESULT: If Hydrogen is present, the gas will burn with a ‘squeaky pop’

EQUATION: 2H2 (g)    +    O2 (g)     →     2H2O (l)

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TEST FOR OXYGEN:

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OXYGEN TEST

Diagram showing the Test for Oxygen

METHOD: Collect gas into a boiling tube Insert glowing splint

RESULT: If Oxygen is present, splint will relight

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TEST FOR CARBON DIOXIDE:

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CARBON DIOXIDE TEST

Diagram showing the Test for Oxygen

METHOD: Bubble gas through limewater Observe colour change

RESULT: If Carbon Dioxide is present, limewater will turn milky and cloudy

EQUATION: Ca(OH)2 (aq)    +    CO2 (g)     →     CaCO3 (s)     +    H2O (l) *White Solid - CaCO3, turns limewater Milky

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TEST FOR AMMONIA:

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AMMONIA TEST

Diagram showing the Test for Ammonia

METHOD: Lower damp red litmus paper or damp universal indicator paper into test solution

RESULT: If Ammonia is present, damp red litmus paper turns Blue If Ammonia is present, damp universal indicator paper turns Purple

EQUATION: NH3 (g)    +    H2O (l)     →     NH4+ (aq)     +    OH- (aq) *Hydroxide ions - OH-, turns litmus Blue

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TEST FOR CHLORINE:

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CHLORINE TEST

Diagram showing the Test for Chlorine

METHOD: Lower damp litmus paper or moist starch-iodide paper into test solution

RESULT: If Chlorine is present, damp litmus paper is bleached White If Chlorine is present, moist starch-iodide paper turns Blue

EQUATION FOR MOIST STARCH - IODIDE PAPER: Cl2 (g)    +    2l- (aq)     →     2Cl- (aq)     +    I2 (aq) *Iodine formed turns the starch Blue

2.45: Describe How to Carry Out a Flame Test

FLAME TEST: Method to identify Metal Cations by the colour of flame they produce

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FLAME TEST

Diagram showing the Flame Test of Metal Cations

METHOD: Platinum or Nichrome wire is cleaned by dipping it into Hydrochloric acid End of wire is dipped into fresh Hydrochloric acid and then into solid sample End of the wire with solid sample attached is placed into a non-roaring, non-luminous bunsen flame Colour of flame is observed and recorded

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

FLAME TEST: Method to identify Metal Cations by the colour of flame they produce

RESULTS:

CATION	COLOUR OF FLAME
Li+	Red
Na+	Yellow
K+	Lilac
Ca2+	Orange-Red
Cu2+	Blue-Green

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

CATIONS: Positively charged ion

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TEST FOR AMMONIUM ION NH4+

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TEST FOR AMMONIUM ION

Diagram showing the Test for Ammonium Ion

METHOD: Add Aqueous Sodium Hydroxide to the solid or solution and heat using bunsen burner Lower damp red litmus paper into gas produced

RESULT: If Ammonium ions are present, pungent-smelling gas is produced Gas produced turns damp red litmus paper Blue

EQUATION:          NH4+ (aq)            +              OH-            →              NH3              +            H2O     Ammonium Ions               Hydroxide Ions (from Solution Tested)   (from Sodium Hydroxide)

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TEST FOR Cu2+, Fe2+ and Fe3+

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TEST FOR Cu2+, Fe2+ and Fe3+
Diagram showing the Test for Cu2+, Fe2+ and Fe3+
METHOD: Add Aqueous Sodium Hydroxide Colour of precipitate is observed and recorded
RESULT AND EQUATION:
METAL CATION	COLOUR OF PRECIPITATE	EQUATION
COPPER (II)      Cu2+	Blue Precipitate	Cu2+    +    2OH-    →    Cu(OH)2
IRON (II)             Fe2+	Green Precipitate	Fe2+    +    2OH-    →    Fe(OH)2
IRON (III)            Fe3+	Brown Precipitate	Fe3+    +    3OH-    →    Cu(OH)3