The Determination of the Mass of a Product of a Chemical Reaction
Objective
Use grams of NaHCO3 and a balanced chemical equation to predict, then verify the grams of NaCl produced.
Brief Overview
We will react sodium bicarbonate with an excess of hydrochloric acid.
NaHCO3 (s) + HCl (aq) → NaCl (aq) + CO2 (g) + H2O (l)
A careful measurement of the mass of NaHCO3 and knowledge of the balanced equation (above) will allow you
to calculate the mass of NaCl expected to be produced. Then, you will measure the actual amount of NaCl you
produced and compare it to the predicted amount.
Safety
1) Make sure to wear goggles during the entire course of the lab, which includes all clean-up time.
2) This lab involves handling hydrochloric acid. This substance is caustic. Be careful to avoid spills, splatter
or inhalation of vapor.
3) If you spill any HCl solution, inform your teacher immediately.
Procedure
Day One - Reacting NaHCO3 with HCl
1) Clean and dry a 150-mL beaker. Place the empty 150-mL beaker on the electronic balance. Record this
value in your data table. Then, press the tare button. The balance will reset to 0.00. If it is slightly off,
wait 3 seconds, then press tare again.
2) Remove the beaker from the balance and add one moderate spoonful of sodium bicarbonate.
3) Return the beaker to the electronic balance and allow the value to become steady. Do not press tare.
Record this value (the mass of sodium bicarbonate) on your data table.
4) Pour about 20 mL of 3-molar hydrochloric acid into a 50 or 100-mL beaker. Place a plastic pipet in the
beaker. DO NOT put the medicine dropper down anywhere but the beaker.
5) Add 3 drops of acid to the NaHCO3 beaker, moving the dropper so that no drops land on each other.
The key point is to spread out the adding of acid so as to hold all splatter within the walls of the beaker.
6) Continue to add acid slowly drop by drop. As liquid begins to build up, gently swirl the beaker. This is
done to make sure unreacted acid reaches unreacted sodium bicarbonate. Do not add acid while
swirling.
7) Your goal is to stop adding acid when all bubbling has ceased. Another way to say that is to add the
minimum amount of HCl that will react with all of the sodium bicarbonate. When you think all bubbling
has ceased, swirl the beaker and check for more bubbling. When you think all bubbling has ceased, add
ONE DROP more of acid and swirl. If no bubbling happens, you are done. DO NOT add more acid.
8) Using a small amount of tape put your initials on the beaker and place it on the tray for an overnight
heating. We will resume the lab on day 2.
9) Throw your disposable pipet in the garbage. Pour any remaining HCl solution down the drain with the
water running. Thoroughly rinse the 100-mL beaker with tap water. Put all glassware away. Wash your
hands.
Day Two - Heating to Constant Weight
1) Weigh your beaker and contents on the electronic balance. Record this weight (first weighing) in your
data table.
2) Set up ring stand, wire gauze and your beaker as shown in the example on the center table and in the prelab discussion. Place a watch glass over the beaker. Using a Bunsen burner, heat the beaker and its
contents for 3 minutes. Allow the beaker to cool.
3) Weigh the beaker and contents (second weighing).
4) Repeat the previous two steps (third weighing).
5) Clean everything thoroughly, washing your hands when finished.
Data Table
Day One Data
Mass
Day Two Data
grams
Mass
empty 150-mL beaker
NaCl plus beaker (heat lamp)
first weighing
NaHCO3 in beaker
NaCl plus beaker (Bunsen burner)
second weighing
grams
NaCl plus beaker (Bunsen burner)
third weighing
Day One Calculations

Based upon the mass of NaHCO3 reacted and the balanced equation given above, calculate the
theoretical mass of NaCl that should form in your reaction (Hint: Do a mass-mass problem starting with the
mass of NaHCO3 in your data table and ending with mass of NaCl).
Day Two Calculations
1) Determine, by subtraction, the actual mass of NaCl produced in your experiment (use the third weighing
– it is the most reliable).
2) Calculate your percentage yield for the reaction.
(% yield = [actual mass of product/theoretical mass of product] x 100).
3) Provide at least one plausible reason why your percent yield did not equal 100 % (in other words, what
happened?)