Chem 106/ Dr. Rusay adapted from Washington State Colleges
Name(s):_________________________________
Stoichiometry / Limiting Reactant / Ideal Gas Law
http://chemconnections.org/general/chem106/106assign.html#CO2
Work in a group of 4. Follow Dr. R’s demonstration and instructions in preparing two volumetric flasks by
placing 30.0 mL 1.09 M (1.09 mol/L) hydrochloric acid (HCl) in each flask, and filling a green balloon with
2.0 g sodium bicarbonate and a blue balloon with 6.0 g sodium bicarbonate. After the reactants have completely
reacted with the cessation of gas and the balloons no longer expand, record your observations below.
Observation (Green))
Observation (Blue)
Provide a plausible explanation for any differences and/or similarities observed in the 2 flasks.
Observe the set of three flasks with balloons attached that have been brought into the lab. As you had done, they
were filled with 30.0 mL 1.09 M hydrochloric acid, HCl (aq). Then the balloons had different amounts of solid
sodium bicarbonate added to the acid: 2.00g NaHCO3 (s) added from the green balloon, 4.00g NaHCO3 (s)
added from the yellow balloon, and 6.00g NaHCO3 (s) added from the blue balloon. When mixed, the sodium
bicarbonate reacted with the acid and produced carbon dioxide, which inflated the balloon in the following
reaction:
_____ HCl (aq) + ____ NaHCO3(s) _____ CO2(g) + _____ H2O(l) + _____ NaCl (aq) hydrochloric acid sodium bicarbonate 1. a. Balance the above equation.
1.b. Record your observations of what you see in the flasks.
Observation (Green))
Observation (Yellow)
Observation (Blue)
1.c. Using your observations, if possible, identify the limiting reactant in each flask. Record the name of
the limiting reactant and its formula in the table below. If you cannot determine which was limiting write
NA.
Limiting Reactant (Green
Limiting Reactant (Yellow)
Limiting Reactant (Blue)
Rank the flasks in order of the amount of CO2 produced, using > (more than), < (less than), = equal
___Green____
___Yellow_____
___Blue_____
2. Calculate the number of moles of sodium bicarbonate that were added to the respective flasks. (The
moles of hydrochloric acid in all 3 flasks is equal to its molarity (1.09 mol / L) x 30.0 ml x 1.00 L / 1,000.
mL)
Moles of NaHCO3 in Green:_________________________
Moles of NaHCO3 in Yellow: ________________________
Moles of NaHCO3 in Blue: ________________________
Divide the moles of NaHCO3 and mol HCl by their respective stoichiometric coefficients from the balanced equation. Compare them and circle the colored balloons above in which the HCl is the limiting reactant. 3. Calculate the number of moles of CO2 produced, which is the same in each flask and then calculate the
respective theoretical volume of CO2 produced in each flask assuming STP (Standard Temperature and
Pressure). Using the Ideal Gas Law show a clear, labeled example of your calculation to the right for any
one of the 3 flasks.
Volume of CO2 in Green:________________________
Volume of CO2 in Yellow: _______________________
Volume of CO2 in Blue:_______________________
4. If unreactive sodium bicarbonate is seen in any of the flasks, calculate the amount left over. If there is
none, write none. Show a clear, labeled example of your calculation for one of the flasks with left over
sodium bicarbonate.
The amount left over in each flask, which should agree with your qualitative observations:
Amount remaining in Green:_________________________
Amount remaining in Yellow:_________________________
Amount remaining in Blue:_________________________