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 probablyrecognize 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:(9 marks, C)

Sample / Amount of
Ethyne / Air / Observations / Diagram of Observations
after Gas Test
1 / 1/1 /
2 / 1/2 /
3 / 1/3 /
4 / 1/12 /

Discussion Questions

  1. Write the BALANCED, including the states, chemical reaction for the production of ethyne, C2H2 , from CaC2 and water.

(2 marks, I)

  1. 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 theBALANCEDchemical 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

  1. Describe some applications of acetylene in industry. (4 marks,A)