Anions Qualitative Analysis - Part 1

Anions Part 1

• This lecture covers carbonate/bicarbonates and sulfur-containing anions.
• Salts are ionic compounds formed from the assembly of anions and cations.
• Anions are negative ion fragments in a salt, contributed by acids.
• Cations are positive ion fragments in a salt, contributed by bases.

Anions Qualitative Analysis

• Anion identification relies on dry and wet reactions, along with specific and selective reactions for each anion.
• Dry reactions involve treating solid salts with acids to identify volatile products, such as carbon dioxide (effervescence).
• Wet reactions involve reacting salt solutions with reagents, resulting in color changes, precipitation, or oxidation-reduction reactions.

Carbonates and Bicarbonates

• Carbonates and bicarbonates are salts of carbonic acid.
• Carbonate is CO₃^2-.
• Bicarbonate is HCO₃^-.
• All carbonate salts are insoluble except alkali (Na, K, Li) and ammonium carbonate.
• Alkali (Na, K, Li), Ammonium, and alkali earth (Mg, Ba, Ca, Sr) bicarbonates are soluble in water.
• Dry reaction with dilute HCl causes effervescence, creating CO2 gas in carbonates and bicarbonates.
• Wet reaction with BaCl₂ solution produces a precipitate.

Sulfur-Containing Anions

• Sulfide (S^2-)
• Sulfite (SO₃^2-)
• Thiosulfate (S₂O₃^2-)
• Sulfate (SO₄^2-)
• Persulfate (S₂O₈^2-)

Dry Reactions - Addition of Dilute HCl

• Sulfides: H₂S evolves on heating.
  • Detection: rotten egg odor, darkening of lead acetate paper, or cadmium acetate paper.
• Sulfites: SO₂ evolves; detected by burnt sulfur odor, and turbidity in limewater.
• Thiosulfates: No immediate change on cold; turbid solution on warming because of H₂S₂O₃ decomposition.
• Sulfates: No reaction with dilute HCl.
• Persulfates: No reaction on cold, decomposes to form oxygen (O) on boiling.

Wet Reactions - Reaction with BaCl₂

• Sulfides: No reaction.
• Sulfites: White precipitate (BaSO₃) which in soluble in dilute HCl
• Thiosulfates: No precipitate on cold; precipitate (BaS₂O₃) upon boiling.
• Sulfates: White precipitate (BaSO₄) that is insoluble in dilute HCl.
• Persulfates: White precipitate (BaSO₄) on boiling.

Wet Reactions - Reducing Action, with Iodine (I₂) and KMnO₄ solution

• Sulfides, sulfites, and thiosulfates act as reducing agents in reactions with iodine and permanganate
• The results include: decolorization, turbidity and different color changes

Special Tests and Spot Tests

• Sulfides: Cadmium carbonate reacts with sulfides to form CdS; canary yellow precipitate.
• Thiosulfates: A blood-red color of ferric thiocyanate complex is created by heating with KCN solution, NaOH, acidification and FeCl3 addition.
• Sulfates: Sulfate is reduced to sulfide by heating a mixture of sulfate, Sodium Carbonate and charcoal in a reducing flame. brownish black stain forms on a silver coin when tested.

Analysis Of Mixtures

• Procedures for identifying mixtures containing various sulfur-containing anions.
  • Separation methods and identifying techniques for individual anions are detailed.

Additional Information

• Contact information for the lecturer

This quiz covers the fundamentals of anions, including carbonate/bicarbonate and sulfur-containing anions. You'll explore the methods for identifying anions through both dry and wet reactions. Test your understanding of the characteristics of salts and the role of anions in ionic compounds.