Chemistry 11 Lab #11

Precipitation


Station #1 Making a known molarity solution
    You will be making a 30 mL sample of a 0.1 M solution of lead nitrate, Pb(NO3)2, or potassium iodide, KI, (ask me which). You will need to calculate the amount (mass)    of solute you will need before proceeding.  The calculation is similar to the one from the last assignment.

  1. Mass out the correct amount of solute you will need. Put it in a 250 mL beaker.
  2. Add enough bottled water needed to make your specified sample.
Step #2 Precipitation: Mixing lead nitrate (Pb(NO3)2 ) and potassium  iodide (KI)
    Use the solutions made in step 1.

  1. Put 15 mL of lead nitrate solution in a 250 mL beaker.
  2. Add an equal amount of potassium iodide and note what happens.
  3. After allowing the mixture to sit for a few minutes while you mass a sheet of filter paper.
  4. Filter what is in the beaker using a glass funnel, ringstand, glass rod, filter paper and beaker.  Note what you get.  Can you explain this?  (Hint: lead iodide, PbI2, is a yellow solid that is very insoluble in water.)  
  5. Spread the filter paper out to dry in a safe, warm place.
  6. Mass the dried paper and whatever was filtered by it.
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