When you are making a ham and cheese sandwich, you need two slices of bread and one piece of ham and cheese. How many complete sandwiches could you make if you had eight slices of ham, seven slices of cheese and eighteen slices of bread? Obviously, there is not enough cheese to make use of all of the ham available. There is some cheese to make some sandwiches but not enough cheese to use up all of the ham. If there was more cheese, you would get more sandwiches. Since you would run out of cheese for the sandwiches, the cheese becomes your limiting reagent and the ham and bread becomes your excess reagents.
Two slices of bread + 1 piece of cheese + 1 piece of ham = 1 ham and cheese sandwich
Similarly, in many reactions, one reactant becomes entirely consumed and the other reactant is left over. The reactant that becomes consumed is called the limiting reagent. When the limiting reagent is all consumed, no more product can be formed (reaction complete). The reactant limits the amount of product that can be formed. In the sandwich analogy above the bread, cheese and ham are not just analogies for the reactants; they also represent the number of moles or particles available for reaction. As soon as one reactant is consumed, the reaction stops because there are no longer particles of that reactant available for reaction. The reaction is limited by the availability of this reagent.
In this experiment, you will predict and observe a limiting reactant during the copper (II) chloride oxidation. You will use the single displacement reaction of aluminum with aqueous copper (II) chloride.
2Al(s) + 3CuCl2(aq) → 3Cu(s) + 2AlCl3(aq)
Copper (II) chloride, CuCl2, turns a light blue in aqueous solution. This is due to the Cu2+(aq) ion. Aluminum chloride is colourless in aqueous solution.
Copper is mankind’s oldest metals, dating back more than 10,000 years. The copper (II) chloride oxidation reaction has been used in petroleum industries for sweetening (a...