Chemistry 11 Lab #12

Lab #12: Synthesis and Decomposition Reactions

.

Theory
Synthesis reactions are of the form: X + Y ---> XY
Decomposition reactions are of the form: XY ---> X + Y
In a balanced equation the total number of atoms of each element match on the left (reactant) and right (product) side of the equation for the reaction.
We can convert from mass to moles and back by using: molar mass = mass/moles
where the molar mass is found from the periodic table.
The balanced equation allows us to use the moles of one substance to find the moles of the other substances (reactants and products) by using ratios.




Part #1 Magnesium metal (Mg) reacts with atmospheric oxygen (O2)

  1. Write the balanced equation for the reaction. (The product is MgO, a white powder.) What kind of reaction is it?
  2. Mass the sample of magnesium metal I give you. Describe the sample. What properties does it share with other metals? How many moles of magnesium is it? Given that the earth's atmosphere contains about 1018 moles of oxygen gas, which reactant is in excess and which is limiting? How many moles of magnesium oxide should it form? What is the theoretical yield in grams?
  3. Ignite the magnesium and allow it to completely burn. Save the white powder formed on a sheet of paper. DO NOT LOOK AT THE FLAME. IT COULD BLIND YOU. Mass the paper and powder, then discard the powder and mass the paper. What is the actual yield? Percent yield? Explain why you got these results.
Part #2 Hydrogen bicarbonate (H2CO3) reacts

  1. Open a bottle of bubbly water (hydrogen bicarbonate solution) and take a sample of the gas given off. Do a flame/splint test to see if the gas is oxygen (flame reignites), hydrogen (a small pop occurs) or carbon dioxide (the splint extinguishes). (We may do this as a group.)
  2. Write a balanced equation for the reaction. What kind of reaction is it?
  3. Place a small amount of the bubbly water in a plastic up and place it on the electronic balance. Note the resulting readings and explain.
Part #3 Iron (III) oxide (Fe2O3) reacts

  1. Place a small sample of iron oxide in a test tube and heat it over a flame. Note the color of the initial product any changes that occur. Pour the still hot powder out onto the metal ring stand base and again note any changes.
  2. Write a balanced reaction for what you think occurs in the first and second parts.
  3. If time permits, try to devie a way of confirming your explanation above using the elctronic balance. Check with me and then try it out.
Hosted by www.Geocities.ws

1