Experiment # 4: Decomposition of a Compound

Heat energy can sometimes be used to break apart a chemical compound. This can provide a chemist with important information about the chemical makeup of a compound. In this lab you will decompose a compound called sodium chlorate. One product that is produced is oxygen gas. You will collect the oxygen gas to determine its properties and density. You will also measure the mass of gas produced and determine the percentage by mass of oxygen in it.

Procedure

  1. Measure and record the mass of a clean and dry medium sized test tube.
  2. Measure 1.00 grams of sodium chlorate and put into the test tube. Record the total mass of the test tube and sodium chlorate.
  3. Clamp the test tube to a rod or ring stand. Setup a hose assembly and gas-collecting bottle. You will use water displacement with a bucket to collect the gas.
  4. When everything has been setup heat the sodium chlorate slowly at first. It should melt and begin to bubble. Heat with a strong flame until no more gas is produced. Wear your goggles!
  5. When no more gas is produced turn off the burner and immediately remove the hose from the water. Allow the test tube to cool.
  6. Place a glass square over the bottle and remove the bottle from the water being careful not to spill any water.
  7. You will now test the gas collected with a glowing and burning wood splint. Remove the glass square. Light a wood splint and then blow it out so that it is glowing. Hold it into the gas in the bottle but do not drop the splint into the bottle. Record your observations. Repeat the test, but with a burning splint.
  8. Determine the volume of gas produced. Do this by filling the space in the bottle with tap water and measuring the amount of water it takes to fill the bottle.
  9. When the test tube has cooled. Measure and record the mass. Clean the test tube with tap water and return the equipment.

Experiment # 4: Decomposition of a Compound

Heat energy can sometimes be used to break apart a chemical compound. This can provide a chemist with important information about the chemical makeup of a compound. In this lab you will decompose a compound called sodium chlorate. One product that is produced is oxygen gas. You will collect the oxygen gas to determine its properties and density. You will also measure the mass of gas produced and determine the percentage by mass of oxygen in it.

Procedure

  1. Measure and record the mass of a clean and dry medium sized test tube.
  2. Measure 1.00 grams of sodium chlorate and put into the test tube. Record the total mass of the test tube and sodium chlorate.
  3. Clamp the test tube to a rod or ring stand. Setup a hose assembly and gas-collecting bottle. You will use water displacement with a bucket to collect the gas.
  4. When everything has been setup heat the sodium chlorate slowly at first. It should melt and begin to bubble. Heat with a strong flame until no more gas is produced. Wear your goggles!
  5. When no more gas is produced turn off the burner and immediately remove the hose from the water. Allow the test tube to cool.
  6. Place a glass square over the bottle and remove the bottle from the water being careful not to spill any water.
  7. You will now test the gas collected with a glowing and burning wood splint. Remove the glass square. Light a wood splint and then blow it out so that it is glowing. Hold it into the gas in the bottle but do not drop the splint into the bottle. Record your observations. Repeat the test, but with a burning splint.
  8. Determine the volume of gas produced. Do this by filling the space in the bottle with tap water and measuring the amount of water it takes to fill the bottle.
  9. When the test tube has cooled. Measure and record the mass. Clean the test tube with tap water and return the equipment.

Calculations

Show all work for your calculations.

  1. What happened to the mass of the sodium chlorate after heating? This mass change represents the mass of the oxygen. Determine the mass of oxygen from the sodium chlorate.
  1. Calculate the percentage of oxygen in the sodium chlorate. Use the mass of oxygen and the mass of the original sodium chlorate.
  1. Calculate the theoretical percentage of oxygen in sodium chlorate. The formula for sodium chlorate is NaClO3. Use your periodic table and atomic masses for the elements to get the total mss of oxygen in the formulas and the total mass of the formula. Use these masses to get the percentage of oxygen in the formula. How does this theoretical percentage compare to your lab result?
  1. What volume of oxygen gas was collected? Find the density of the oxygen gas with correct units.
  1. Was this process a chemical of physical change? Explain your answer.
  1. Give some chemical and physical properties of oxygen.

Write a formal conclusion.

Calculations

Show all work for your calculations.

  1. What happened to the mass of the sodium chlorate after heating? This mass change represents the mass of the oxygen. Determine the mass of oxygen from the sodium chlorate.
  1. Calculate the percentage of oxygen in the sodium chlorate. Use the mass of oxygen and the mass of the original sodium chlorate.
  1. Calculate the theoretical percentage of oxygen in sodium chlorate. The formula for sodium chlorate is NaClO3. Use your periodic table and atomic masses for the elements to get the total mss of oxygen in the formulas and the total mass of the formula. Use these masses to get the percentage of oxygen in the formula. How does this theoretical percentage compare to your lab result?
  1. What volume of oxygen gas was collected? Find the density of the oxygen gas with correct units.
  1. Was this process a chemical of physical change? Explain your answer.
  1. Give some chemical and physical properties of oxygen.

Write a formal conclusion.