Overview
This lecture covers the classification of acids, bases, and salts as strong, weak, or non-electrolytes, and demonstrates identification using conductivity and pH measurement.
Electrolyte Classification
- Electrolytes in solution are classified as strong, weak, or non-electrolytes.
- Strong electrolytes (SE) dissociate 100% into ions (example: HCl).
- Weak electrolytes (WE) partially dissociate and exist in equilibrium (example: acetic acid, CH₃COOH).
- Non-electrolytes (NE) do not dissociate into ions (example: methanol, CH₃OH).
Conductivity and Light Bulb Experiment
- Strong electrolytes produce a brightly lit bulb, indicating high conductivity.
- Weak electrolytes cause a dim bulb due to partial ionization.
- Non-electrolytes do not light the bulb since no ions are present.
- Distilled water, sucrose, and methanol are non-electrolytes (no light).
- Tap water is a weak electrolyte (dim light due to few ions).
- Potassium chloride (KCl), hydrochloric acid (HCl), potassium hydroxide (KOH), sodium nitrate (NaNO₃), magnesium chloride (MgCl₂), copper sulfate (CuSO₄), and sulfuric acid (H₂SO₄) are strong electrolytes (bright light).
- Acetic acid and ammonium hydroxide are weak electrolytes (dim light).
pH Determination Using Indicator Strips
- pH strips indicate solution acidity or basicity by color change.
- Tap water has a neutral pH of 7.
- 0.1 M nitric acid and hydrochloric acid have a low pH (around 1).
- 0.1 M acetic acid and apple juice have a pH of about 3 (acidic).
- 0.1 M potassium chloride has a pH around 6 (close to neutral).
- 0.1 M sodium carbonate and ammonium hydroxide have a pH of 10 (basic).
- 0.1 M potassium hydroxide is strongly basic with pH of 14.
Key Terms & Definitions
- Electrolyte — substance that dissolves in water to produce ions and conduct electricity.
- Strong Electrolyte (SE) — compound that dissociates completely into ions in solution.
- Weak Electrolyte (WE) — compound that partially dissociates, existing in equilibrium with its ions.
- Non-electrolyte (NE) — substance that does not produce ions in solution.
- Dissociation — process where compounds split into ions in solution.
- pH — measure of acidity or basicity of a solution (0–14 scale).
- Aqueous (aq) — dissolved in water.
Action Items / Next Steps
- Ensure use of protective equipment during lab work.
- Practice classifying substances based on conductivity and pH results.
- Review chemical formulas and dissociation behavior for common acids, bases, and salts.