Molar Concentration Lab
Purpose:
Measured volumes of HCl acid solution are allowed to react with a (mostly) insoluble substance,
CaCO3. By measuring the mass of insoluble material dissolved as a result of this reaction, the
number of moles of acid is determined based on the stoichiometric relationship between the
acid and the CaCO3.
Safety Concerns:
HCl (hydrochloric acid) is corrosive. The hydrogen gas produced can be explosive if exposed to
flame. Hot plates can burn. Goggles and aprons are required.
Procedure:
1. Determine the mass of clean 250.0 mL to the nearest 0.1 g and record this mass in a data
table.
2. Add 4 or 5 marble chips to the beaker and determine the mass of beaker and chips to the
nearest 0.1 g and record in a data table.
3. Obtain a volume of HCl(aq) between 40 and 60 mLs. Record the volume used to the nearest
0.1 mL and then pour this acid in the beaker with the marble chips.
4. Heat the mixture on a hot plate at about 50ºC. You will notice bubbling streaming from the
marble chips. Continue heating until this reaction stops.
5. Decant and discard the solution which remains in the beaker.
6. Wash the marble chips two or three times with distilled water, decanting the rinse water and
disposing down drain.
7. Dry the marble residue according to instructions given by the teacher. Use hot glove to
remove beaker as it will be hot.
8. Write your initials on your beaker and set it on designated shelf to dry until next block we
meet. When the residue is dry, determine the mass of the beaker and chips to the nearest 0.1 g
and record in data table.
Data:
Create a data table based on the requirements for this lab.
Questions and Analysis:
1. Write the balanced chemical equation for the reaction between the hydrochloric acid (HCl)
and the marble chips. The chips are calcium carbonate (CaCO3). The products are H2O, CO2,
and H2. Be sure to include the states (aq, g, l, etc.). What type of reaction is this?
2. Calculate the mass lost due the reaction of the chips.
3. Convert the mass lost (#2) to moles CaCO3.
4. Based on the mole ratio of moles CaCO3 to moles HCl, how many moles of HCl were present in
the added liquid?
5. Based on the moles of HCl present (#4) and the volume of the liquid you recorded, what is
the molarity of the HCl solution? (Molarity = mol/L)