The phenomenon you observed involves the behavior of two different salts—ammonium chloride (NH₄Cl) and sodium trioxocarbonate (IV) (sodium bicarbonate, NaHCO₃, or sodium carbonate, Na₂CO₃)—in water and the resulting effects on litmus paper, which is a pH indicator.
Ammonium Chloride (NH₄Cl)
-
Dissolution in Water: When ammonium chloride dissolves in water, it dissociates into its constituent ions: \[ NH₄Cl (s) \rightarrow NH₄^+ (aq) + Cl^- (aq) \]
-
Formation of NH₄⁺: The ammonium ion (NH₄⁺) is a weak acid that can donate a proton (H⁺) to water, forming hydronium ions (H₃O⁺): \[ NH₄^+ + H₂O \leftrightarrow H₃O^+ + NH₃ \]
-
Effect on Litmus Paper: The presence of hydronium ions increases the acidity of the solution, resulting in a pH lower than 7. Since red litmus paper turns red in acidic conditions (pH < 7), the solution will turn blue litmus paper red.
Sodium Trioxocarbonate (IV) (Sodium Bicarbonate or Sodium Carbonate)
-
Dissolution in Water: When sodium bicarbonate or sodium carbonate dissolves in water, it dissociates into its constituent ions: \[ NaHCO₃ (s) \rightarrow Na^+ (aq) + HCO₃^- (aq) \quad \text{or} \quad Na₂CO₃ (s) \rightarrow 2Na^+ (aq) + CO₃^{2-} (aq) \]
-
Formation of HCO₃⁻ or CO₃²⁻: The bicarbonate ion (HCO₃⁻) can act as a weak base and can react with water to produce hydroxide ions (OH⁻): \[ HCO₃^- + H₂O \leftrightarrow H₂CO₃ + OH^- \] The carbonate ion (CO₃²⁻) is a stronger base and also accepts protons from water, contributing to an increase in hydroxide ions: \[ CO₃^{2-} + H₂O \leftrightarrow HCO₃^- + OH^- \]
-
Effect on Litmus Paper: The formation of hydroxide ions increases the pH of the solution above 7, making it basic. Blue litmus paper will remain blue, but red litmus paper will turn blue in basic conditions (pH > 7).
Summary
- Ammonium chloride is acidic when dissolved in water, resulting in a solution that turns blue litmus paper red.
- Sodium trioxocarbonate (bicarbonate or carbonate) is basic when dissolved in water, resulting in a solution that turns red litmus paper blue.
This highlights the different acid-base properties of the two compounds when they interact with water.