Comprehensive Qualitative Analysis and Reactions of Anions

Systematic Analysis and Qualitative Reactions of Carbonates

• Reaction with Dilute Hydrochloric Acid ($\text{HCl}$):

  • Experimental Procedure: To a small portion of the salt, add dilute hydrochloric acid ($\text{HCl}$).
  • Observations: Brisk effervescence occurs along with the liberation of a colourless, odourless gas.
  • Inference: Indicates the presence of carbonate ($\text{CO}_3^{2-}$).
  • Chemical Equation: $\text{MCO}_3 + 2\text{HCl} \rightarrow \text{MCl}_2 + \text{H}_2\text{O} + \text{CO}_2$

• Confirmatory Lime Water Test:

  • Experimental Procedure: The evolved gas is passed through lime water ($\text{Ca(OH)}_2$) contained in a test tube, and the mixture is shaken well.
  • Observations: Brisk effervescence with the liberation of a colourless, odourless gas occurs, causing the lime water to turn milky.
  • Inference: Presence of carbonate ($\text{CO}_3^{2-}$) is confirmed.
  • Chemical Equation: $\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}$

Qualitative Analysis and Reactions of Acetates

• Reaction with Dilute Sulfuric Acid ($\text{H}_2\text{SO}_4$):

  • Experimental Procedure: A small portion of the salt is rubbed with dilute sulfuric acid ($\text{H}_2\text{SO}_4$).
  • Observations: A characteristic smell of vinegar ($\text{CH}_3\text{COOH}$) is detected.
  • Inference: Indicates the presence of acetate ($\text{CH}_3\text{COO}^-$).
  • Chemical Equation: $\text{CH}_3\text{COOM} + \text{H}_2\text{SO}_4 \rightarrow \text{CH}_3\text{COOH} + \text{MHSO}_4$

• Confirmatory Reaction with Ferric Chloride ($\text{FeCl}_3$):

  • Experimental Procedure: A small portion of the salt is boiled with ferric chloride ($\text{FeCl}_3$) solution.
  • Observations: Formation of a red precipitate.
  • Inference: Presence of acetate ($\text{CH}_3\text{COO}^-$) is confirmed.
  • Chemical Equations: $3\text{CH}_3\text{COO}^- + \text{FeCl}_3 \rightarrow (\text{CH}_3\text{COO})_3\text{Fe} + 3\text{Cl}^-$$(\text{CH}_3\text{COO})_3\text{Fe} + 2\text{H}_2\text{O} \rightarrow (\text{CH}_3\text{COO})(\text{OH})_2\text{Fe} + 2\text{CH}_3\text{COOH}$

Qualitative Identification and Reactions of Chlorides

• Reaction with Concentrated Sulfuric Acid ($\text{H}_2\text{SO}_4$) and Ammonium Hydroxide ($\text{NH}_4\text{OH}$):

  • Experimental Procedure: A small quantity of the salt is boiled with a few drops of concentrated sulfuric acid ($\text{H}_2\text{SO}_4$) and warmed. When gas is evolved, a glass rod dipped in ammonium hydroxide ($\text{NH}_4\text{OH}$) is brought near the mouth of the test tube.
  • Observations: A colourless gas having a pungent smell is evolved. Dense white fumes are formed near the mouth of the test tube upon bringing the glass rod dipped in $\text{NH}_4\text{OH}$.
  • Inference: Indicates the presence of chloride ($\text{Cl}^-$).
  • Chemical Equations: $\text{H}_2\text{SO}_4 + \text{Cl}^- \rightarrow \text{HSO}_4^- + \text{HCl}$$\text{NH}_4\text{OH} + \text{HCl} \rightarrow \text{NH}_4\text{Cl} + \text{H}_2\text{O}$

• Reaction with Manganese Dioxide ($\text{MnO}_2$) and Concentrated Sulfuric Acid:

  • Experimental Procedure: A portion of the salt is heated with a little manganese dioxide ($\text{MnO}_2$) and concentrated $\text{H}_2\text{SO}_4$.
  • Observations: Evolution of a greenish-yellow gas with a pungent smell.
  • Inference: Presence of chloride ($\text{Cl}^-$) is confirmed.
  • Chemical Equation: $3\text{H}_2\text{SO}_4 + 2\text{Cl}^- + \text{MnO}_2 \rightarrow \text{MnSO}_4 + 2\text{HSO}_4^- + 2\text{H}_2\text{O} + \text{Cl}_2$

• Confirmatory Silver Nitrate Test ($\text{AgNO}_3$):

  • Experimental Procedure: A small portion of the salt is treated with dilute nitric acid ($\text{HNO}_3$), boiled, cooled, and then silver nitrate ($\text{AgNO}_3$) solution is added.
  • Observations: A curdy white precipitate is formed.
  • Inference: Presence of chloride ($\text{Cl}^-$) is confirmed.
  • Chemical Equations: $\text{MCl} + \text{AgNO}_3 \rightarrow \text{AgCl} + \text{MNO}_3$$\text{NaCl} + \text{AgNO}_3 \rightarrow \text{AgCl} + \text{NaNO}_3$

Identification and Confirmatory Reactions of Nitrates

• Reaction with Concentrated Sulfuric Acid ($\text{H}_2\text{SO}_4$) and Paper Ball:

  • Experimental Procedure: To a small portion of the salt, concentrated $\text{H}_2\text{SO}_4$ is added, warmed, and a paper ball is introduced into the test tube.
  • Observations: Evolution of a reddish-brown gas.
  • Inference: Indicates the presence of nitrate ($\text{NO}_3^-$).
  • Chemical Equations: $2\text{NO}_3^- + \text{H}_2\text{SO}_4 \rightarrow \text{SO}_4^{2-} + 2\text{HNO}_3$$4\text{HNO}_3 + \text{C} \rightarrow 4\text{NO}_2 + 2\text{H}_2\text{O} + \text{CO}_2$

• Reaction with Concentrated Sulfuric Acid ($\text{H}_2\text{SO}_4$) and Copper Turnings:

  • Experimental Procedure: To a small portion of salt, add concentrated $\text{H}_2\text{SO}_4$ and warm the solution. To the hot solution, copper turnings are added.
  • Observations: Evolution of a reddish-brown gas.
  • Inference: Presence of nitrate ($\text{NO}_3^-$) is confirmed.
  • Chemical Equations: $2\text{NO}_3^- + \text{H}_2\text{SO}_4 \rightarrow \text{SO}_4^{2-} + 2\text{HNO}_3$$4\text{HNO}_3 + \text{Cu} \rightarrow \text{Cu(NO}_3)_2 + 2\text{H}_2\text{O} + 2\text{NO}_2$

• Confirmatory Brown Ring Test:

  • Experimental Procedure: To a small portion of the salt solution, freshly prepared ferrous sulphate ($\text{FeSO}_4$) solution is added. The mixture is cooled, and concentrated $\text{H}_2\text{SO}_4$ is carefully added along the sides of the test tube.
  • Observations: A brown ring is formed at the junction of two liquids.
  • Inference: Presence of nitrate ($\text{NO}_3^-$) is confirmed.
  • Chemical Equations: $\text{NO}_3^- + \text{H}_2\text{SO}_4 \rightarrow \text{HSO}_4^- + \text{HNO}_3$$6\text{FeSO}_4 + 3\text{H}_2\text{SO}_4 + 2\text{HNO}_3 \rightarrow 3\text{Fe}_2(\text{SO}_4)_3 + 4\text{H}_2\text{O} + 2\text{NO}$$\text{FeSO}_4 + \text{NO} + 5\text{H}_2\text{O} \rightarrow [\text{Fe}(\text{H}_2\text{O})_5\text{NO}]\text{SO}_4$

Qualitative Reactions and Identification of Sulphates

• Barium Chloride Test:

  • Experimental Procedure: To a small quantity of the salt solution, add barium chloride ($\text{BaCl}_2$) solution.
  • Observations: Formation of a white precipitate that is insoluble in dilute hydrochloric acid ($\text{HCl}$).
  • Inference: Indicates the presence of sulphate ($\text{SO}_4^{2-}$).
  • Chemical Equation: $\text{M}_2\text{SO}_4 + \text{BaCl}_2 \rightarrow \text{BaSO}_4 + 2\text{MCl}$

• Lead Acetate Test:

  • Experimental Procedure: To a small portion of the salt solution acidified with dilute acetic acid ($\text{CH}_3\text{COOH}$), lead acetate solution ($(\text{CH}_3\text{COO})_2\text{Pb}$) is added.
  • Observations: Formation of a white precipitate.
  • Inference: Presence of sulphate ($\text{SO}_4^{2-}$) is confirmed.
  • Chemical Equation: $\text{SO}_4^{2-} + (\text{CH}_3\text{COO})_2\text{Pb} \rightarrow \text{PbSO}_4 + 2\text{CH}_3\text{COO}^-$