Mole Relationship in a Chemical Reaction
Name_______________________________
30 Points
Period______ Date____________________
INTRODUCTION: Chemists can determine the equation for a chemical reaction by identifying the type
and amount of the substances involved. The coefficients for the balanced equation can be determined by
converting mass values to moles and expressing the moles values in terms of small whole number ratios.
It is not always practical to determine mass values for all the substances involved in the reaction,
particularly if gases are produced. Therefore, chemists will often use only the mass values for one of the
reactants and one of the products. By incorporating knowledge of the Law of Conservation of Mass, the
balanced equation can be determined.
In this experiment you will react sodium hydrogen carbonate (baking soda), NaHCO3, with
hydrochloric acid, HCl, to form sodium chloride, NaCl, and two gaseous products. You will determine
the mole relationship between NaHCO3 and NaCl, and use this data along with the Law of Conservation
of mass to predict a balanced equation for this reaction.
OBJECTIVES: In this experiment you will
 react a known mass of NaHCO3 with excess HCl
 calculate the mole relationship between NaHCO3 and NaCl
 predict a balanced equation for the reaction, and
 calculate the % yield and the % error of the actual product produced
EQUIPMENT:
goggles
Spoon
Bunsen Burner
apron
watch glass
striker
evaporating dish
HCl dropper
oven
balance
baking soda
PROCEDURE:
1. Clean and dry an evaporating dish. Do not wash it unless necessary. If you do wash it, heat it
strongly for 2-3 minutes in a Bunsen burner flame and allow it to cool. Determine the mass to the
nearest 0.001g.
2. With a spoon, add about 3.000 g of sodium hydrogen carbonate, NaHCO3, to the evaporating
dish. It does not need to be exactly 3.000 g, but should be measured precisely.
1
3. Cover the evaporating dish with a watch glass. Use the 6 M HCl dropper and add about
6 mL (1 mL = 20 drops) CAUTION: HCl causes burns; avoid skin and eye contact. Rinse
spills with plenty of water. Allow the drops to enter the lip of the evaporating dish so that
they gradually flow down the side as shown in Figure 11-1.
4. Continue adding the acid slowly until the reaction has stopped. Do not add more acid than
is needed.
5. Tilt the dish from side to side to make sure the HCl has reached all of the NaHCO3, if any
unreacted NaHCO3 remains, add a few more drops of HCl to complete the reaction. Remove
the watch glass cover with forceps and rinse the underside of the watch glass with a very small
amount of distilled water from the water bottle. Be careful to wash all the material into the
evaporating dish as shown in Figure 11-2.
6. Return the watch glass to your drawer, write your and you partner’s name on a paper towel,
and place the evaporating dish on the paper towel on the tray on the front lab bench.
You should be able to complete the 1st three in the data table and questions #1, 3-6. One of the
gases produced will extinguish a flame, the other is a vapor of a common liquid.
7. After the product has been allowed to evaporate overnight, weigh the product to the nearest
0.001g.
9. Complete the data table and questions #1 and #2 and then check your answers with your teacher.
Then the contents of the evaporating dish may be rinsed down the drain with plenty of water.
DATA TABLE: Measure to the nearest 0.001g.
A.
mass of empty evaporating dish
___________g
B.
mass of evaporating dish and NaHCO3
___________g
C.
mass of NaHCO3
___________g
D.
mass of evaporating dish and NaCl
___________g
E.
mass of NaCl
___________g
QUESTIONS:
1. Calculate the number of moles of NaHCO3 used in this reaction:
2. Calculate the number of moles of NaCl produced in this reaction:
3. Write a complete balanced equation for the reaction that occurred. (see the introduction)
2
4. From your balanced equation, what is the mole ratio between NaHCO3 and NaCl? How does this
compare with your mole ratio from questions #1 and #2. Give a reason why they are similar or different.
5. Suppose you started with 3.25 moles of sodium hydrogen carbonate, how many moles of sodium
chloride would you expect to be formed? If you started with X moles of NaHCO3 how many moles
of NaCl would you expect to be formed? Explain.
6. Using the mass of sodium bicarbonate, calculate the number of grams of sodium chloride that should
have been produced. This is the expected (experimental or theoretical) yield.
7. Calculate the % yield for NaCl produced in the experiment, by comparing it to the amount of NaCl
that should have been recovered.
% Yield 
actual
x 100% 
expected
8. Calculate the % error for NaCl produced in the experiment, by comparing it to the amount of NaCl
that should have been recovered.
% Error 
expected - actual
x 100% 
expected
3