DP1 Gunpowder: Ideal Mixture

Ingredients for gunpowder is readily available in a secondary school laboratory. Not only that, it can be made and safely set off in the safety of a secondary school laboratory as well.

The video below is that of six different compositions of the ingredients set off in a fume hood. The girls were competing against the boys. The reaction in this instance was initiated by using a fuse made of filter paper soaked in concentrated solution of potassium nitrate and dried. Watch the movie for the results.

Here are the questions:

  1. What are the ingredients of gunpowder? (There are three.)
  2. There are two chemical reactions taking place in the process. The first one is the one taking place on the fuse and the other between the ingredients of gunpowder. Can you suggest chemical equations for those two reactions? Balance them.
  3. Both the reactions are redox reactions. Identify the oxidizing and reducing agents in each of the reactions.
  4. What was the competition? In other words, what was the criteria on which their mixture was being judged?
  5. What factors affect the duration for which the flame lasts and the height of the flame? In other words, what determines the efficiency of the reaction? How could you determine the duration of the reaction and the height of the flame using the video?
  6. What other measurements could be made to determine the relative efficiency of the reaction of the different mixtures?
  7. If you had to prepare a 10.0g mixture of the ingredients so that it produced as high a flame as possible, what would be the composition? Justify your choice of composition.
  8. Determine how much gas would be produced by your mixture.
  9. Why does a bullet containing these ingredients, when set off, produce an explosion?
  10. Design an investigation that studies the relationship between the composition and one of the factors below:
  • flame size (height?)
  • duration for which the mixture burns
  • efficiency of the reaction
  • (or one of your choosing)

In your design, also indicate how you would analyze the data to determine the experimental ratio that produces the best results.

Concepts involved:

  • reduction, oxidation, complete combustion, incomplete combustion, oxidizing agent, reducing agent.
  • stoichiometry, molar ratio, stoichiometric ratio, limiting regent, excess reagent.
  • rate of reaction.

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