Overview
This laboratory demonstration shows how to measure the pH of a saturated calcium hydroxide solution using a wireless pH probe and calculate the hydroxide ion concentration from the pH reading.
Objective
- Determine the concentration of dissolved calcium hydroxide by measuring pH
- Calculate pOH from the measured pH value
- Assess hydroxide ion concentration in the saturated solution
Equipment and Materials
- Wireless pH probe connected to phone or device
- Pre-calibrated pH meter
- Saturated calcium hydroxide solution (previously prepared and confirmed via Tyndall effect)
- Squeeze bottle with deionized water
- Kimwipes for gentle cleaning
- Waste bottle for rinse water
- Small beaker for sample testing
- Buffer solution for probe storage
Procedure
| Step | Action |
|---|
| 1 | Transfer calcium hydroxide solution into small beaker |
| 2 | Remove pre-calibrated pH probe from storage |
| 3 | Rinse probe thoroughly with deionized water |
| 4 | Gently wipe probe with Kimwipes |
| 5 | Slowly insert probe into saturated solution |
| 6 | Allow probe to stabilize and record pH reading |
| 7 | Rinse probe with deionized water after measurement |
| 8 | Wipe probe clean and return to buffer solution |
Results
- Measured pH: 12.45
- Solution confirmed as strongly basic
- Probe reading stabilized with minimal fluctuation
Key Concepts
- pH measurement determines hydroxide ion concentration in basic solutions
- Saturated calcium hydroxide dissociates into calcium and hydroxide ions
- pOH can be calculated from pH using: pH + pOH = 14
- Gentle handling prevents pH probe damage and ensures accurate readings
- Proper probe maintenance requires rinsing and storage in buffer solution