Combustion of Acetylene
Large granules of Calcium Carbide
Scoop or spatula to handle the calcium carbide
3 large test tubes of similar size with stoppers (held in large empty beaker)
Wooden splint and lit candle
Large beaker (500mL to 1L) half full of water
1. In this lab we will produce acetylene by placing calcium carbide (CaC2) in water. Write the chemical formula for the reaction between calcium carbide and water knowing that the product is acetylene (C2H2).
2. The acetylene in this lab will be collected in a test tube and burned. Write the balanced equation for the combustion of acetylene.
3. Look at the balanced equation. Note the coefficients of the reactants. What proportion of oxygen molecules are required for the most effective burning of acetylene.
Procedure Summary and Important INFO:
The beaker is filled with water. A calcium carbide granule is dropped in the water in the container and bubbles of acetylene gas begin to be produced. If a test tube full of water is inverted and placed over the evolving gas the gas displaces the water and the entire test tube fills with acetylene. The test tube can be stoppered to retain the gas. Evidence of any black soot produced indicates that there is not enough oxygen present for complete combustion to occur. If the test tube is pulled out before the water is fully displaced we can get a test tube partially filled with acetylene as oxygen will rush in to replace the water.
In the steps that follow you will be filling 3 test tubes with different amounts of acetylene.
Diagram of gas collection:
1. Fill a test tube with water and invert into the large beaker. Try to minimize air bubbles at the top of the test tube. Your teacher can show you a trick!
2. Drop a piece of calcium carbide into the beaker and place the mouth of the test tube over the calcium carbide in order to