Mass Relationships in a Chemical Reaction (Mass-to-Mass Conversions)
Problem: Measure the amount of carbon dioxide and sodium chloride produced by the
reaction of a measured amount of sodium hydrogen carbonate with hydrochloric acid and
compare this data with the theoretical amount.
Materials Needed:
 Sodium hydrogen carbonate
 Hydrochloric Acid (6M)
 Test tube
 50 ml beaker
 Medicine Dropper
 Watch Glass
 Centigram balance
Discussion: A law of chemistry states that a given chemical reaction will produce a certain,
definite amount of products from a given amount of reactants. If only one chemical
reaction occurs and if the reaction is complete, the amounts of products can be calculated
from the amounts of reactants. In this experiment we will verify this law.
Sodium hydrogen carbonate and hydrochloric acid react completely to form carbon
dioxide, sodium chloride and water (according to the following equation):
NaHCO3 + HCl  NaCl + CO2 + H2O
If we have a known amount of pure sodium hydrogen carbonate and it reacts with
sufficient hydrochloric acid, we should be able to predict the amount of each of the
products formed from what we learned in the class lecture.
We also want to verify these calculations by experiment. We must measure he mass of the
CO2 from the weight loss of the reaction mixture, because CO2 is a gas. Evaporating the
water and weighing the residue can measure the mass of the sodium chloride.
Procedure:
 Weigh a small test tube and record the weight. Place 1.2-1.5 g of pure NaHCO3 in the
test tube and reweigh to the nearest hundredth of a gram. The difference between
the two weights is the mass of your sample.
 Place 10-15 ml of HCl in a 50 ml beaker and, together with your medicine dropper,
place it on the balance. Weigh and record the weight of everything together
(including test tube)
 Remove the test tube and add a drop or two of hydrochloric acid from the beaker to
it. Mix the contents by flicking the test tube and note the bubbles of CO2 escaping.
Continue adding HCl until no more bubbles are observed. Replace EVERYTHING on
the balance and reweigh. The difference between this weight and the previous one
is the mass of CO2 lost.


Weigh and record the weight of a watch glass. Carefully pour the contents of the
test tube into the watch glass. Rinse the test tube with a few milliliters of water
from a wash bottle and add the rinsing to the watch glass.
Evaporate the solution in the watch glass by pacing it on a beaker of boiling water.
When all the water has evaporated weigh the watch glass and the sodium chloride
and compute the mass of NaCl by difference.
Data:
Weight of test tube + NaHCO3
Weight of test tube
Weight of NaHCO3
Weight of test tube + beaker + HCl, dropper
(before mixing)
Weight of test tube + beaker + dropper and
solutions (after mixing)
Weight of CO2
Weight of watch glass + NaCl
Weight of watch glass
Weight of NaCl
Calculations: Calculate the theoretical amount of CO2 and NaCl that should be obtained
from your sample of NaHCO3. Compare the actual amounts of products with the theoretical
amounts and calculate percent yield.