Chalk Bubbles

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Page ID: 128792

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Required Training	Required PPE
UC Lab Safety Fundamentals	Lab coat, safety glasses/goggles, nitrile gloves

Equipment	Chemicals
Two pieces of chalk	15 mL 2 N HCl
Two 5” diameter watch glass or crystalizing dish	15 mL 2 N Acetic acid

Procedure:

Put a piece of chalk into each of the two reaction vessels.
Pour the weak acid over the first chalk and note the reaction rate
Pour the strong acid over the second chalk and notice the reaction rate

Discussion:

The reaction proceeding is between calcium carbonate and the acids used have the formulas:

CaCO₃ + 2 HCl → CO₂ + H₂O + CaCl₂

CaCO₃ + 2 H(C₂H₃O₂) → CO₂ + H₂O + Ca(C₂H₃O₂)₂

Hazards:

If you should need to, pour dilute basic first aid solution on any affected areas before washing with copious amounts of water. Always wear protective clothing when showing demos, especially with corrosives

SOP:

Corrosive – Acetic Acid, Hydrochloric Acid

Disposal (by Storeroom):

This demo can be rinsed down the drain with water if it is within pH 4-10, or transported back to the dispensary where we will neutralize it and do the same.