Identity of a Carbonate
Name:
Purpose:
Identify an unknown solid as sodium carbonate, magnesium carbonate, or
aluminum carbonate by reacting the solid with hydrochloric acid (HCl(aq)).
Prelab Questions:
1. Write the formulas for sodium carbonate, magnesium carbonate, and
aluminum carbonate.
2. Recall that when H2CO3 is produced it decomposes into H2O(l) and CO2(g).
a. Write the equation for solid sodium carbonate reacting with
aqueous HCl.
b. Write the equation for solid magnesium carbonate reacting with
aqueous HCl.
c. Write the equation for solid aluminum carbonate reacting with
aqueous HCl.
3. In this experiment, you will react 1.00 g of the unknown solid. Use your
equations above and fenceposting to answer the following questions.
Show your fenceposts (3 fenceposts per question).
a. For each solid, if 1.00 g reacts, what mass of CO2 will be produced?
b. For each solid, if 1.00 g reacts, what mass of the chloride will be
produced?
c. For each solid, if 1.00 g reacts, what volume of HCl(aq) will react?
(The HCl has a concentration of 1 mol HCl per liter of solution.)
4. Put your answers to question 3 in the following table.
Carbonate
formula
CO2
Produced (g)
chloride
produced (g)
HCl
Reacted (mL)
5. Which of the three measurements do you think would be the most reliable
for distinguishing between the three solids? Explain.
6. In the lab, how could you measure the three things in the table (g CO2, g
chloride, mL HCl)? Explain.
Procedure:
1. With an electric scale and weighing boat, obtain 1.00 g of the unknown
solid. Place the solid in a medium Erlenmeyer flask.
2. In a 50-mL graduated cylinder, obtain approximately 30 mL of 1 M HCl.
Record the exact volume.
3. With a pipet, slowly add the HCl to the solid in the flask. It will bubble as
CO2 is produced.
4. Continue adding HCl slowly until the reaction is complete—until no more
bubbles are produced. Try not to add any excess HCl, and return any
unused HCl in the pipet to the graduated cylinder.
5. Record the volume of HCl remaining and determine how much HCl was
used.
6. Repeat the experiment for a total of 3 trials.
Data:
In the space below, construct a clear, logical data table to record your results.