20,345
edits
Changes
Created page with "==Key Stage 4== ===Meaning=== '''Testing for aqueous ions''' is a set of techniques used to identify the ions in a compound. ===About Testing For Aqueous Ions=== Aq..."
==Key Stage 4==
===Meaning===
'''Testing for aqueous ions''' is a set of techniques used to identify the [[ion]]s in a [[compound]].
===About Testing For Aqueous Ions===
[[Aqueous]] [[ion]]s can be identified through [[Chemical Reaction|chemical reaction]]s which [[product|produce]]:
*A [[precipitate]] - Which can indicate [[Metal Ion]]s, [[Halide]] [[ion]]s or [[Sulphate]] [[ion]]s.
*A [[gas]] - [[Carbon Dioxide]] [[gas]] indicates [[Carbonate]] [[ion]]s.
: [[Metal Ion]]s are [[Positive Ion]]s and referred to as [[Cation]]s because they would collect at the [[Cathode]] in an [[electrolysis]] [[Chemical Reaction|reaction]].
: There are many different [[Negative Ion]]s and these are referred to as [[Anion]]s because they would collect at the [[Anode]] in an [[electrolysis]] [[Chemical Reaction|reaction]].
===Testing for Aqueous Metal Cations===
To test for [[aqueous]] [[metal]] [[cation]]s is done by adding [[Sodium Hydroxide]] to the [[solution]].
The following [[Chemical Reaction|reaction]]s occur to [[product|produce]] identifiable [[precipitate]]s:
====Iron(II) Ions====
<chem>FeCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Fe(OH)2(s)</chem>
: A light green [[precipitate]] is formed.
====Iron(III) Ions====
<chem>FeCl3(aq) + 3NaOH(aq) -> 3NaCl(aq) + Fe(OH)3(s)</chem>
: A red-brown [[precipitate]] is formed.
====Copper(II) Ions====
<chem>CuCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Cu(OH)2(s)</chem>
: A light blue [[precipitate]] is formed.
====Magnesium, Calcium and Aluminium Ions====
<chem>MgCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Mg(OH)2(s)</chem>
<chem>CaCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Ca(OH)2(s)</chem>
: Both [[product|produce]] a white [[precipitate]] but can then be identified with a [[Flame Test]].
<chem>AlCl3(aq) + 3NaOH(aq) -> 3NaCl(aq) + Al(OH)3(s)</chem>
: A white [[precipitate]] is formed but can be distinguished form [[Magnesium]] and [[Calcium]] by adding excess [[Sodium Hydroxide]] which causes the [[precipitate]] to [[dissolve]].
===Testing for Aqueous Anions===
===Meaning===
'''Testing for aqueous ions''' is a set of techniques used to identify the [[ion]]s in a [[compound]].
===About Testing For Aqueous Ions===
[[Aqueous]] [[ion]]s can be identified through [[Chemical Reaction|chemical reaction]]s which [[product|produce]]:
*A [[precipitate]] - Which can indicate [[Metal Ion]]s, [[Halide]] [[ion]]s or [[Sulphate]] [[ion]]s.
*A [[gas]] - [[Carbon Dioxide]] [[gas]] indicates [[Carbonate]] [[ion]]s.
: [[Metal Ion]]s are [[Positive Ion]]s and referred to as [[Cation]]s because they would collect at the [[Cathode]] in an [[electrolysis]] [[Chemical Reaction|reaction]].
: There are many different [[Negative Ion]]s and these are referred to as [[Anion]]s because they would collect at the [[Anode]] in an [[electrolysis]] [[Chemical Reaction|reaction]].
===Testing for Aqueous Metal Cations===
To test for [[aqueous]] [[metal]] [[cation]]s is done by adding [[Sodium Hydroxide]] to the [[solution]].
The following [[Chemical Reaction|reaction]]s occur to [[product|produce]] identifiable [[precipitate]]s:
====Iron(II) Ions====
<chem>FeCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Fe(OH)2(s)</chem>
: A light green [[precipitate]] is formed.
====Iron(III) Ions====
<chem>FeCl3(aq) + 3NaOH(aq) -> 3NaCl(aq) + Fe(OH)3(s)</chem>
: A red-brown [[precipitate]] is formed.
====Copper(II) Ions====
<chem>CuCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Cu(OH)2(s)</chem>
: A light blue [[precipitate]] is formed.
====Magnesium, Calcium and Aluminium Ions====
<chem>MgCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Mg(OH)2(s)</chem>
<chem>CaCl2(aq) + 2NaOH(aq) -> 2NaCl(aq) + Ca(OH)2(s)</chem>
: Both [[product|produce]] a white [[precipitate]] but can then be identified with a [[Flame Test]].
<chem>AlCl3(aq) + 3NaOH(aq) -> 3NaCl(aq) + Al(OH)3(s)</chem>
: A white [[precipitate]] is formed but can be distinguished form [[Magnesium]] and [[Calcium]] by adding excess [[Sodium Hydroxide]] which causes the [[precipitate]] to [[dissolve]].
===Testing for Aqueous Anions===