Chemistry Lab
Name___________________________ Hr____
Introduction to Stoichiometry
Background:
The reaction of a carbonate with an acid is a common chemical reaction. You may have
witnessed the reaction between acetic acid, commonly called vinegar, and sodium
bicarbonate, commonly called baking soda, in a middle school volcano experiment.
The reaction of sodium bicarbonate(NaHCO3) with hydrochloric acid(HCl) is a convenient
reaction to use in studying relationships in chemical equations. It is convenient because the
reaction is fairly rapid and produces three products: sodium chloride, water, and carbon
dioxide gas. The only product that remains in the beaker after evaporation or heating is
sodium chloride. You will need to determine the balanced equation for the reaction before
you can compare how the amount of sodium bicarbonate reacted compares to the amount
of sodium chloride produced. In this experiment the volume of HCl is not specifically
measured out, instead it is added until all of the sodium bicarbonate is completely reacted.
Thus, sodium bicarbonate is the limiting reactant.
Procedure:
Day 1
1.
2.
3.
4.
Obtain safety goggles to wear during entire lab.
Label a clean, dry 100 mL beaker with your name and class hour.
Find the mass of the beaker and record it on the data table.
Carefully add about 3 grams sodium bicarbonate. Record the mass of the beaker and
sodium bicarbonate in the data table.
5. Add three drops of methyl orange indicator to the beaker. [This substance is yellow in
the presence of a base and turns red in the presence of an acid]
6. Using a pipet, slowly add 3 M hydrochloric acid. It is important that you add the acid
slowly so that the reaction does not over flow and ruin your data. Swirl the reaction until you
see a color change from yellow to red. Continue adding acid and swirling until the red
color remains for 20 seconds and all the solid has reacted.
7. Place your beaker in the fume hood until the next lab period, in order to allow the water
to evaporate.
Day 2
1. Measure the mass of the beaker with the dry solid, sodium chloride. Record the mass.
2. Wash out your beaker and put it away.
Data:
Mass of beaker
Mass of beaker and sodium bicarbonate
Mass of beaker and dry sodium chloride
Calculations:
Be sure to show all work, include all units, and circle answers!
1. a) How many grams of sodium bicarbonate
reacted in the experiment?
b) Convert the grams sodium bicarbonate
to moles :
2. a) How many grams of sodium chloride
were produced in the experiment?
b) Convert the grams of sodium chloride
to moles:
4. Calculate the experimental mole ratio for moles of sodium chloride produced to moles of
sodium bicarbonate reacted.
5. Write the balanced equation for the double replacement reaction between sodium
bicarbonate and hydrochloric acid:
6. Write the balanced equation for the reaction that actually occurred (see the
background section). Circle the product that produced "fizzing".
7. According to the balanced equation, what is the ratio of moles of sodium chloride to
moles of sodium carbonate?
8. The experimental mole ratio in #4 should be the same as the equation ratio in #7. Explain
any experimental error that could have caused a different ratio.
9. The hydrochloric acid is the excess reactant; sodium bicarbonate is the limiting reactant.
Explain what these terms mean.
10. Describe one scientific thing learned that you did not know prior to this experiment.