Caroline Imreibe

Reaction in a cylinder - Orange Stuff - Rust

Concept: A precipitation will result from a double replacement reaction among Sodium carbonate and iron chloride.

Materials:

500- or 1000-mL glass cylinder

Water

Spoonful of sodium carbonate (about 2-5 g)

Funnel

Filter paper

1-2 g iron (III) chloride

Procedure:

1.) Fill glass cylinder with water to top.

2.) Sprinkle spoonful of sodium carbonate into water.

3.) Place funnel with filter paper inside the cylinder. Add a few milliliters of water to filter paper to remove any solution from the graduate in the stem of the funnel.

4.) Add 1-2 g of iron (III) chloride to the filter paper in the funnel. Next add a few mL of water to dissolve the solid and carry it down the stem of the funnel.

Introduction:

What do you think will happen when I mix this solution with this yellow powder? Will the powder sink or float? (add iron chloride).

Explanation: When the iron (III) chloride travels down the stem of the funnel and is added to the solution below, it reacts with the sodium carbonate solution forming a mixture of iron hydroxide and iron carbonate precipitate. This orange precipitate should start to sink in the solution. During this precipitation reaction, a secondary reaction also occurs in which some of the iron ions react with water to form an acid, which in turn reacts with the carbonate ions to produce CO₂ gas. This has the effect of pushing the precipitate up in the solution rather than having it sink.

FeCl₃ + Na₂CO₃--> Fe₂(CO₃)₃

CO₃^-2 + H₂0 --> OH^- + Fe⁺³ --> Fe(OH)₃

Fe⁺³ + H₂0 ---> H⁺ + CO₃^-2 ---> CO₂

Safety: Handle wet glassware cautiously.

Waste Disposal: Dispose solution into sink.

Reference: de Vos, Wobbe, Using Large Glass Cylinders To Demonstrate Chemical Reactions, J. Chem. Educ. 1999, 76, 528. (April 1999)