Lecture Notes

Experiment on Solutions and Conductivity

Key Definitions

• Electrolyte: A substance that dissolves to form a solution containing ions, thus conducting electricity.

Objective

• To understand the nature of different aqueous solutions (sodium chloride, hydrochloric acid, acetic acid, glucose, and tap water) by observing their ability to conduct electricity.

Experiment Setup

• A simple device with copper electrodes and a light bulb was used.
• The light bulb glows if the solution conducts electricity, indicating the presence of ions.

Solutions Tested

1. 0.1 M Sodium Chloride (NaCl) - Table Salt

   • Observation: Light bulb glowed brightly.
   • Conclusion: The solution contains a large number of ions (Na⁺, Cl⁻).

2. 0.1 M Hydrochloric Acid (HCl)

   • Observation: Light bulb glowed brightly.
   • Conclusion: The solution contains a large number of ions (H⁺, Cl⁻).

3. 0.1 M Acetic Acid (CH₃COOH) - Vinegar

   • Observation: Light bulb glowed dimly.
   • Conclusion: Few ions present; solution mainly consists of acetic acid molecules.

4. 0.1 M Glucose (C₆H₁₂O₆) - Sugar

   • Observation: Light bulb did not glow.
   • Conclusion: No ions in the solution; purely molecular.

5. Tap Water

   • Observation: Light bulb glowed very faintly.
   • Conclusion: Contains few ions (e.g., sodium, calcium, magnesium) responsible for faint glow and hard water characteristics.

Summary Table of Results

| Solution | Light Bulb | Conclusion | |---------------------|------------|---------------------------------| | NaCl | Brightly | Mainly ions | | HCl | Brightly | Mainly ions | | Acetic Acid | Dimly | Few ions, mostly molecules | | Glucose | Not at all | No ions, only molecules | | Tap Water | Faintly | Very few ions, hard water ions |

Practical Classifications of Solutes

• Strong Electrolytes

  • Exist exclusively as ions in solution.
  • Strongly conducting solutions.
  • Examples: Sodium chloride, hydrochloric acid, sodium hydroxide.

• Weak Electrolytes

  • Exist as an equilibrium mixture of ions and molecules in solution.
  • Weakly conducting solutions.
  • Examples: Acetic acid, hydrofluoric acid, ammonia.

• Non-Electrolytes

  • Exist exclusively as molecules in solution.
  • Non-conducting solutions.
  • Examples: Sugar, methanol, acetone.

Conclusion

• This experiment helps classify substances based on their ionic presence in solution and their electrical conductivity, providing insights into their chemical reactions and behavior in aqueous environments.