How to Find Oxygen in Silver Oxide

Silver oxide is a compound composed of silver and oxygen atoms. It decomposes to silver and oxygen under high heat. The oxygen gas is driven off during the reaction, leaving the silver metal behind. The Lomonosov-Lavoisier law, also known as the law of conservation of mass or matter, states that matter in a closed system cannot be created or destroyed, but is simply transformed from one state to another. This means that the mass of the reactants in a chemical reaction must be equal to the mass of the products. Therefore one can determine the mass of oxygen in the original sample by subtracting the weight of the silver produced at the end of the reaction from the mass of the original sample of silver oxide. This reaction is best done under a reducing atmosphere.

Things You'll Need

  • Bunsen burner
  • Silver oxide
  • Crucible
  • Crucible lid
  • Tongs
  • Analytical balance
  • Paper
  • Pen
  • Wire triangle
  • Tripod
  • Protective eyewear
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Instructions

  1. Determine the Mass of Oxygen in the Sample

    • 1

      Put on your protective eyewear.

    • 2

      Place the wire triangle on the tripod and light the Bunsen burner.

    • 3

      Place a clean, dry crucible on the wire triangle and heat the crucible for several minutes until it turns a dull, red colour.

    • 4

      Using the tongs, remove the crucible from the heat and allow to cool completely. This should take approximately ten minutes. Be very careful when handling the hot crucible.

    • 5

      Weigh the cool crucible on an analytical balance to the nearest 0.001g. Record the weight. Do not touch the crucible with your fingers.

    • 6

      Place the silver oxide sample in the crucible.

    • 7

      Weigh the crucible and silver oxide and record the weight.

    • 8

      Place the crucible back on the wire frame and gradually heat the silver oxide for ten minutes. You may partially cover the crucible with the lid during heating. Take care not to inhale the fumes coming off the sample.

    • 9

      Increase the heat on the Bunsen burner to full capacity and heat for a further ten minutes.

    • 10

      Turn off the flame and allow the crucible to cool completely. This should take approximately ten more minutes.

    • 11

      Weigh the cooled crucible on the analytical balance. Record the weight.

    • 12

      Repeat the above steps until a constant weight is observed; that is, until further heating of the sample produces no change in the recorded weight, at which point the reaction can be considered complete.

    Derive the Percent Composition of Silver and Oxygen in the Sample

    • 13

      Calculate the mass percent of silver in the sample using the weights you recorded in the previous section: (weight of silver/weight of silver oxide)x 100.

    • 14

      Calculate the mass percent of oxygen in the sample: (weight of oxygen/weight of silver oxide)x 100.

    • 15

      Calculate the moles of silver: (mass percent silver/atomic mass silver).

    • 16

      Calculate the moles of oxygen: (mass percent oxygen/atomic mass oxygen).

    • 17

      Calculate the ratio of moles of silver to moles of oxygen: (moles silver/moles oxygen).

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