Mahopac High School
SAT Chemistry
Mole Relationship in a Chemical Reaction
In a balanced chemical equation, all reactions and products must be represented by
symbols or formulas. The total number of atoms of each element must be the same on
each side of the balanced equation to satisfy the Law of Conservation of Matter and
Energy.
From the molecular mass (mw) of a reactant or product, we can convert the actual mass
of the substance taking part in the reaction to moles of the substance. The mole
relationship given by the coefficients of the balanced equation lets us calculate the
theoretical number of moles of all substances taking part in the reaction.
In this experiment, a known amount of sodium hydrogen carbonate (sodium bicarbonate)
NaHCO3 reacts with 6M (six molar)hydrochloric acid HCl. We can calculate from the
balanced chemical equation the amount of sodium chloride (NaCl) that should be
produced. The theoretical amount will be compared to the actual amount recovered in
lab and a percent error will be calculated.
Procedure:
1) Weigh a clean, dry evaporation dish.
2) Tare out the scale and weigh out between 2 and 3 grams of NaHCO3 in the dish.
3) Cover the evaporating dish with a watch glass to prevent splattering and loss of
material during the next step.
4) Using a dropper pipet, slowly add 6M HCl to the dish through the opening at the spout
and gently swirl as demonstrated by the instructor. BE VERY CAREFUL WITH THE
HCl. Continue adding HCl and gently swirling until the reaction has stopped.
5) Tilt the watch glass over the dish and use a few more drops of HCl to insure all the
NaHCO3 has reacted.
6) GENTLY heat the evaporating dish until the contents are dry.
7) Allow the dish to cool and weigh.
8) Reheat the dish and contents STRONGLY and recalculate mass. If the mass changed
more than 0.02g, repeat another heating.
9) Calculate the mass of the dry contents.
10) Rinse everything carefully with plenty of water.
Conclusion:
1) Write a balanced chemical equation for the reaction in the lab.
2) Show all calculations, and FLM, to calculate the theoretical yield of NaCl.
3) Calculate the % error between the experimental yield and the theoretical yield.
4) Compare the experimental mole ratio to the theoretical mole ratio of NaHCO3:NaCl.