Mass-Mass Relationships in Reactions
Purpose: To compare the theoretical mass of one of the products of a double replacement reaction
to the experimentally determined mass of the same product.
Equipment
Balance
Graduated cylinder, 100-mL
Beakers, 250-mL (2)
Beaker, 100-mL
Stirring rod
ring stand
iron ring
funnel
safety glasses
Materials
Lead (II) nitrate (Pb(NO3)2
Potassium iodide (Kl)
Filter paper
Procedure
1. Using the balance, measure out exactly 1.1g of lead (II) nitrate (Pb(NO3)2). Record this
mass as (a) in your data table.
2. Place the Pb(NO3)2 in a clean 250-mL beaker and add 50.0mL water. Stir thoroughly to
make sure all crystals are dissolved. Rinse off the stirring rod.
3. Measure out approximately 1.2g of potassium iodide (Kl). Place it in a clean 100mL
beaker and add 50.0mL of water. Stir until all crystals are dissolved.
4. Pour the Kl solution into the 250-mL beaker containing the Pb(NO3)2 solution. Stir.
Record your observations as (d) in your data table. When you stir be careful not to be
messy.
5. Find the mass of a piece of filter paper. Record this as mass (b). Fold the filter paper and
place it in the funnel as shown in Figure 28-1. Pour slowly. Do not allow the liquid to rise
above the edge of the filter paper in the funnel. Stir with each pouring to get as much
solid out as you can each time.
6. Rinse the beaker with about 20mL of water. Pour the rinse water through the filter.
Repeat the rinsing and filtering until all the precipitate is out of the beaker.
7. Wash the precipitate by pouring about 10mL of clean water through the filter.
8. Remove the filter paper and precipitate from the funnel and place in an oven or in your
lab drawer to dry. Use 2 paper towels, put your name on them and put the solid in the
fume hood.
Tomorrow
9. Mass the dry precipitate + filter paper (mass © in our data table)
10. While you are waiting for the solution to filter, write a balanced reaction for the
experiment you are performing. Remember all lead compounds are precipitates. Then do
problem numbers 3-7
CONCLUSIONS AND QUESTIONS
How many grams of precipitate should you make?
What is another name for a double replacement reaction?
Give a brief general description of a double replacement reaction. What must one of the
products of such a reaction be in order to perform an experiment such as this one?
Suggest some possible sources of error in this experiment
Define the terms filtrate, and precipitate and limiting reactant, and excess reactant.
Determine a percent error based on the grams of PbI2 you should have produced and how
much you did produce. Define theoretical yield and actual yield.