Lab Activity: Complete and Incomplete Combustion of Ethyne
Name:__________________
Partner’s Name:__________
Date of Lab:_____________
Date Due: ______________
(1 mark, C)
Hydrocarbons are covalently bonded compounds and are often used as fuels. You probably recognize
some of the more familiar names such as methane, propane, butane and octane. In this activity you will
produce a hydrocarbon called ethyne (acetylene) which is often used in welding torches. When it combines with
oxygen it produces a very hot flame that can melt certain metals. When acetylene combusts in excess pure
oxygen it produces carbon dioxide and water. This is called complete combustion. However, if there is not
enough oxygen supplied during combustion carbon monoxide and carbon soot can be produced as well as
carbon dioxide and water. This is called incomplete combustion.
In this activity you will react calcium carbide, CaC 2 , with water to produce ethyne gas. Calcium
hydroxide is also produced in this reaction. You will collect different amounts of ethyne gas in different test
tubes and then light it on fire so that a combustion reaction occurs. You should observe both complete and
incomplete combustion in this lab.
Purpose
The purpose of this lab is to____________________________________________________________________
___________________________________________________________________________________________
______________________________________________________________________________(2 marks, C)
Materials
Bunsen burner
Wooden splints
Tweezers/ scoopula
4 test tubes with no cracks or tape
1 250mL beaker
Tap water
Calcium carbide lumps
Safety
List all safety precautions should you take when working with a Bunsen burner. (2 marks, C)
List all safety precautions should you take when working with heated glass. (2 mark, C)
List all safety precautions should you take when working with calcium carbide. (3 marks, C)
Method
1. Invert a test tube full of water into a beaker of water, making sure that no water r4uns out of the test
tube.
2. Use the tweezers or scoopula to place a few small pieces of calcium carbide into the beaker. Observe
the bubbles rising from the calcium carbide. These bubbles are ethyne gas.
3. Place the inverted test tube over the calcium carbide and completely fill the test tube with ethyne gas.
4. Remove the test tube from the water and place it mouth down on the lab bench so that the gas does
not escape.
5. Repeat step 3 three more times with the other test tubes this time filling ½, 1/3 and 1/12 of the test
tube with acetylene, respectively.
6. Lift each tube from the water, always keeping them inverted. Allow air to replace the water that urns
out of the test tubes.
7. Place you8r thumb over the end of each test tube and shake each tube for 20 seconds to mix the air and
ethyne. Place each test tube mouth down on the lab bench.
8. One at a time, hold each test tube horizontally and bring a burning splint close to its mouth. Wait until
each reaction is complete and then place the test tube back down on the lab bench. Observe each test
tube carefully and complete the observation table.
Observations
Table 1:
Sample
(9 marks, C)
1
Amount of
Ethyne / Air
1/1
2
1/2
3
1/3
4
1/12
Observations
Diagram of Observations
after Gas Test
Discussion Questions
1. Write the BALANCED, including the states, chemical reaction for the production of ethyne, C2H2 , from
CaC2 and water.
(2 marks, I)
2. What did you observe as the amount of oxygen in each test tube increased?
(1 mark, I)
4. a) In which tube(s) did complete combustion occur? Explain how you know.
(2 marks, I)
b) Write the BALANCED chemical equation for the complete combustion of ethyne, including the states.
(3 marks, I)
5. a) In which test tube(s) did incomplete combustion occur? Explain how you know.
(2 marks, I)
b) Write the BALANCED chemical equation for the incomplete combustion of ethyne, including the states.
(3 marks, I)
6. Ethyne is covalently bonded. Draw the Lewis structure to show the bond arrangement in this molecule.
(2 marks, I)
Application
7. Describe some applications of acetylene in industry.
(4 marks,A)