What accidents o r errors may occur i n the following experiment? Standardisation o f Sodium Hydroxide Stock Solution with Potassium Hydrogen Phthalate Purpose The purpose o f this experiment i s t o standardise a stock solution o f NaOH b y creating a primary standard such a s potassium hydrogen phthalate. You will have t o calculate the exact concentration i n moles per litre o f your NaOH stock solution. The molecular mass o f K H C 8 H 4 O 4 i s 2 0 4 . 2 3 g m o l – 1 .
Answer
Possible Accidents and Errors in the Standardisation of Sodium Hydroxide with Potassium Hydrogen Phthalate
🧪 Experimental Errors
- Incorrect weighing of potassium hydrogen phthalate (KHP) due to balance inaccuracy or air drafts.
- Incomplete transfer of KHP from the weighing boat to the titration flask can lead to concentration miscalculation.
- Errors in titration endpoint detection if phenolphthalein is used as an indicator — over- or under-titration may occur.
- NaOH is hygroscopic (absorbs CO2 from air), which can lower its actual concentration, leading to inaccurate standardisation.
- Using dirty or wet glassware can introduce contaminants or dilute the reagents, especially the NaOH solution.
- Parallax errors while reading burette volumes may result in volume inaccuracies.
⚠️ Potential Accidents
Sodium hydroxide is caustic and can cause severe skin and eye burns. Accidental spills or splashes are hazardous.
Inhaling fine KHP powder or NaOH dust during weighing can irritate the respiratory tract.
Mishandling glassware such as burettes or flasks can result in breakage and injury.
• Always wear gloves, goggles, and a lab coat.
• Perform titrations over a white tile to clearly observe the endpoint.
• Keep NaOH solutions tightly sealed to prevent CO2 absorption.
• Rinse burette with NaOH before filling to ensure concentration consistency.
🔍 Conclusion
Accurate standardisation of NaOH using potassium hydrogen phthalate depends on strict adherence to procedural accuracy and lab safety. Both experimental errors and personal safety hazards must be diligently managed to ensure reliable and reproducible results.