Baking Soda and Vinegar: Limiting Reactant Lab
The limiting reactant of a chemical reaction is the substance that places an upper bound on the amount of product that the reaction can produce. The limiting reactant places this upper bound because the reaction must stop once all of the limiting reactant is consumed.
If the relative amount of reactants is altered, then the limiting reactant may change accordingly. For example, a balanced chemical equation of a certain reaction specifies that an equal number of moles of two substances A and B is required. If there are more moles of B than of A, then A is the limiting reactant because it is completely consumed when the reaction stops and there is an excess of B left over. Increasing the amount of A until there are more moles of A than of B, however, will cause B to become the limiting reactant because the complete consumption of B, not A, forces the reaction to cease.
How does increasing the amount of baking soda affect the amount of carbon dioxide produced?
If the amount of baking soda is increased, then the amount of carbon dioxide produced will also increase up to a certain point, at which the amount of carbon dioxide will remain constant because the vinegar has become the new limiting reactant.
Reaction container, such as 500 mL vacuum flask with stopper
Tubing to connect flask to gas collection set up
1000 mL graduated cylinder
Gas collection box
1.Mass out desired amount of baking soda. Each subsequent trial will use one gram more.
2.Put baking soda into reaction vessel.
3.Measure 40 mL vinegar.
4.Completely fill 1000 mL graduated cylinder with water. Half fill the collection box with water. Place hand over the opening of the graduated cylinder, invert the graduated cylinder, and put it in the gas collection box which is partially filled with water.
5.Position gas collecting hose so it runs from reaction vessel through gas collecting box to opening of the graduated cylinder. The idea is that any gas coming through the tube will rise in the graduated cylinder and displace the water in it.
6.Record the amount of air, if any, in the top of the graduated cylinder.
7.Quickly add the vinegar to the reaction vessel and stopper the opening.
8.When the reaction is completed, record the volume of gas in the graduated cylinder. Record observations about which reactant was the limiting reactant.
9.Repeat the procedure with a new mass of baking soda. Before beginning, rinse the reaction vessel with water. Refill the graduated cylinder with water. Check water level in collection box so it has room for the water from the graduated cylinder.
10.Clean up: Rinse reaction vessel, empty collection box, dry table as needed, cleanup up any baking soda spills..
Measurements of volume, measurements of mass, and limiting reactant
Volume of vinegar
Mass of baking soda