PRÁCTICA DE OBTENCIÓN DE ACETILENO | A PARTIR DE CARBURO DE CALCIO Y AGUA

Chemical Reaction of Calcium Carbide and Water

Introduction to the Experiment

• The experiment focuses on obtaining acetylene gas from the reaction between calcium carbide and water. The chemical reaction is highlighted as a key aspect of this practice.

Materials Required

• Essential materials include:

• A hydropneumatic flask.

• A separating funnel for decantation.

• Four test tubes (20 x 200 mm) with stoppers.

• Tweezers, a hose, and a universal support stand with clamps.

• Reactants needed are calcium carbide, potassium permanganate solution, and water for the reaction.

Setting Up the Reaction

• Calcium carbide stones are placed in the separating funnel, followed by adding water while ensuring no leaks occur to prevent gas escape.

• Three pieces of calcium carbide are sufficient for generating an adequate amount of gas. Proper assembly is crucial to avoid losing gas during collection.

Collecting Acetylene Gas

• The method used for collecting acetylene involves water displacement; test tubes must be filled with water beforehand to ensure accurate measurement without air bubbles.

• Air must be purged from hoses before starting the collection process to ensure that only acetylene fills the tubes instead of air. This is done by counting to fifteen while keeping hoses submerged in water.

Observing Gas Production

• Upon opening the valve, an immediate reaction occurs when water contacts calcium carbide, producing bubbles indicative of acetylene formation.

• The first tube fills quickly due to direct contact with reactants; subsequent tubes require additional water flow for continued reactions as they slow down after initial filling. Each tube is capped immediately after filling to prevent gas loss.

Testing Chemical Properties of Acetylene

Combustion Test

• The first tube containing acetylene undergoes combustion testing by introducing heat via a matchstick while ensuring safety precautions are taken (keeping hands away from flame).

• Incomplete combustion results in black residue due to insufficient oxygen supply during burning, indicating that acetylene can combust but may not fully oxidize under certain conditions.

Oxidation Test with Potassium Permanganate

• A small quantity of potassium permanganate is added to another tube containing acetylene; any color change indicates a chemical reaction has occurred.

Chemical Reactions of Acetylene

Reaction with Potassium Permanganate

• The vigorous mixing of acetylene with potassium permanganate is observed, indicating a potential reaction. If the acetylene is not oxidized, the permanganate will reduce and change color due to the formation of manganese dioxide.

• A positive test for acetylene is confirmed as potassium permanganate oxidizes it without converting it into acid, resulting in the formation of brown manganese dioxide.

Reaction with Iodine Solution

• The iodine solution reacts with acetylene gas, leading to a decrease in color intensity, which indicates that iodine has reacted with the acetylene present.

• This reaction is identified as a traditional addition reaction where iodine combines with acetylene, producing a lighter solution compared to the original.

Combustion Tests

• Further tests reveal that unreacted acetylene remains in the tube when mixed with iodine and ignited; this suggests incomplete reactions have occurred.

• Observations show that combustion occurs completely when sufficient oxygen from permanganate is provided, confirming chemical properties of acetylene.

Incomplete Combustion Observations

• The absence of carbon residues after combustion indicates complete burning of acetylene due to adequate oxygen supply from permanganate.

• A fourth tube containing no substances serves as a control for combustion observations. Black soot forms inside due to incomplete combustion caused by insufficient air supply.

Safety Precautions and Energy Release

• Caution is emphasized during reactions involving gases; distance should be maintained while observing energy release during combustion processes.