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Difference between revisions of "GCSE Chemistry Required Practical: Identifying Unknown Compounds"

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====Halide Test====
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The test for [[Halide]] [[anion]]s begins by adding dilute [[Nitric Acid]] to remove any possible [[Carbonate]]s. Then [[Silver Nitrate]] is added to form a [[precipitate]] of [[Silver Halide]].
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#Add four [[spatula]]s of [[Sodium Halide]] to a 50ml beaker with 40ml [[water]] and stir with a [[Glass Rod|glass rod]] to [[dissolve]].
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#Measure roughly 2ml of [[Sodium Halide]] [[solution]] using a [[pipette]].
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#Add the [[solution]] to a [[Test Tube|test tube]].
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#Add 4 drops of 0.4[[Molarity|M]] [[Nitric Acid]] to remove any [[Carbonate]]s.
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#Measure roughly 2ml 0.05[[Molarity|M]] [[Silver Nitrate]] [[solution]] using a clean [[pipette]].
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#Add the [[Silver Nitrate]] to the [[Test Tube|test tube]].
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#Use the following information to identify the [[Halide]] present.
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<chem>NaCl(aq) + AgNO3(aq) -> NaNO3(aq) + AgCl(s)</chem>
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: A white [[precipitate]] is formed.
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<chem>NaBr(aq) + AgNO3(aq) -> NaNO3(aq) + AgBr(s)</chem>
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: A cream coloured [[precipitate]] is formed.
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<chem>NaI(aq) + AgNO3(aq) -> NaNO3(aq) + AgI(s)</chem>
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: A yellow [[precipitate]] is formed.
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====Sulphate Test====
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The test for [[Sulphate]] [[anion]]s begins by adding dilute [[Hydrochloric Acid]] to remove any possible [[Carbonate]]s. Then [[Barium Chloride]] is added to form a [[precipitate]] of [[Barium Sulphate]].
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#Add four [[spatula]]s of [[Metal Sulphate]] to a 50ml beaker with 40ml [[water]] and stir with a [[Glass Rod|glass rod]] to [[dissolve]].
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#Measure roughly 2ml of [[Metal Sulphate]] [[solution]] using a [[pipette]].
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#Add the [[solution]] to a [[Test Tube|test tube]].
 +
#Add 4 drops of 0.4[[Molarity|M]] [[Hydrochloric Acid]] to remove any [[Carbonate]]s.
 +
#Measure roughly 2ml 0.1[[Molarity|M]] [[Barium Chloride]] [[solution]] using a clean [[pipette]].
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#Add the [[Barium Chloride]] [[solution]] to the [[Test Tube|test tube]].
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#If a [[Sulphate]] is present:
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<chem>Na2SO4(aq) + BaCl2(aq) -> 2NaCl(aq) + BaSO4(s)</chem>
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: a white [[precipitate]] is formed.
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 +
====Carbonate Test====
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The test for [[carbonate]] [[anion]]s begins by adding [[Hydrochloric Acid]] to the [[solution]]. This [[product|produces]] a [[gas]] which is collected and bubbled through [[Limewater]] to identify if [[Carbon Dioxide]] has been [[product|produced]]. If [[Carbon Dioxide]] has been [[product|produced]] then the [[Limewater]] will turn from [[transparent]] to cloudy.
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#Add two [[spatula]]s of [[Metal Carbonate]] [[solution]] to a [[Test Tube|test tube]].
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#Measure roughly 2ml of [[Limewater]] [[solution]] using a [[pipette]].
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#Add the [[Limewater]] to a second [[Test Tube|test tube]].
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#Measure 2ml 0.4[[Molarity|M]] [[Hydrochloric Acid]] [[solution]] using a clean [[pipette]].
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#Add the [[Hydrochloric Acid]] [[solution]] to the first [[Test Tube|test tube]] containing the [[Metal Carbonate]] [[Solution]].
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#Immediately attach a [[bung]] with a [[Delivery Tube|delivery tube]] to pass the [[gas]] through the [[Limewater]] in the second [[Test Tube|test tube]].
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<chem>Na2CO3(aq) + 2HCl(aq) -> 2NaCl(aq) + H2O(l) + CO2(g)</chem>
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: A [[gas]] is [[product|produced]] and bubbled through [[Limewater]].
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<chem>CO2(g) + CaO(aq) -> CaCO3(s)</chem>
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: The [[Calcium Carbonate]] makes the [[Limewater]] appear cloudy.
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====Unknown Compound Test====
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To identify an unknown [[Ionic Compound|ionic compound]] use each [[experiment]] mentioned above and record the [[results]] to compare with the expected [[results]] for each [[Metal Compound]].

Revision as of 12:18, 29 January 2019

Key Stage 4

Meaning

Use a variety of chemical tests to identify the ions in ionic compounds.

Method

Flame Test

  1. Dip the end of an Inoculation Loop into concentrated Hydrochloric Acid.
  2. Place the end of the Inoculation Loop into the powdered metal compound.
  3. Hold the end of the Inoculation Loop in a roaring blue Bunsen Burner flame.
  4. Observe and record the colour of the flame.
  5. Use the following table to identify the metal ion.
Metal Ion Flame Colour
Lithium Red
Sodium Orange
Potassium Lilac (Purple)
Calcium Orange-red
Barium Brown-green
Copper Green-blue
Lead Blue

Halide Test

The test for Halide anions begins by adding dilute Nitric Acid to remove any possible Carbonates. Then Silver Nitrate is added to form a precipitate of Silver Halide.

  1. Add four spatulas of Sodium Halide to a 50ml beaker with 40ml water and stir with a glass rod to dissolve.
  2. Measure roughly 2ml of Sodium Halide solution using a pipette.
  3. Add the solution to a test tube.
  4. Add 4 drops of 0.4M Nitric Acid to remove any Carbonates.
  5. Measure roughly 2ml 0.05M Silver Nitrate solution using a clean pipette.
  6. Add the Silver Nitrate to the test tube.
  7. Use the following information to identify the Halide present.

<chem>NaCl(aq) + AgNO3(aq) -> NaNO3(aq) + AgCl(s)</chem>

A white precipitate is formed.

<chem>NaBr(aq) + AgNO3(aq) -> NaNO3(aq) + AgBr(s)</chem>

A cream coloured precipitate is formed.

<chem>NaI(aq) + AgNO3(aq) -> NaNO3(aq) + AgI(s)</chem>

A yellow precipitate is formed.

Sulphate Test

The test for Sulphate anions begins by adding dilute Hydrochloric Acid to remove any possible Carbonates. Then Barium Chloride is added to form a precipitate of Barium Sulphate.

  1. Add four spatulas of Metal Sulphate to a 50ml beaker with 40ml water and stir with a glass rod to dissolve.
  2. Measure roughly 2ml of Metal Sulphate solution using a pipette.
  3. Add the solution to a test tube.
  4. Add 4 drops of 0.4M Hydrochloric Acid to remove any Carbonates.
  5. Measure roughly 2ml 0.1M Barium Chloride solution using a clean pipette.
  6. Add the Barium Chloride solution to the test tube.
  7. If a Sulphate is present:

<chem>Na2SO4(aq) + BaCl2(aq) -> 2NaCl(aq) + BaSO4(s)</chem>

a white precipitate is formed.

Carbonate Test

The test for carbonate anions begins by adding Hydrochloric Acid to the solution. This produces a gas which is collected and bubbled through Limewater to identify if Carbon Dioxide has been produced. If Carbon Dioxide has been produced then the Limewater will turn from transparent to cloudy.

  1. Add two spatulas of Metal Carbonate solution to a test tube.
  2. Measure roughly 2ml of Limewater solution using a pipette.
  3. Add the Limewater to a second test tube.
  4. Measure 2ml 0.4M Hydrochloric Acid solution using a clean pipette.
  5. Add the Hydrochloric Acid solution to the first test tube containing the Metal Carbonate Solution.
  6. Immediately attach a bung with a delivery tube to pass the gas through the Limewater in the second test tube.

<chem>Na2CO3(aq) + 2HCl(aq) -> 2NaCl(aq) + H2O(l) + CO2(g)</chem>

A gas is produced and bubbled through Limewater.

<chem>CO2(g) + CaO(aq) -> CaCO3(s)</chem>

The Calcium Carbonate makes the Limewater appear cloudy.

Unknown Compound Test

To identify an unknown ionic compound use each experiment mentioned above and record the results to compare with the expected results for each Metal Compound.

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