limiting reactant experiment

#General_chemistry_Lab
#limiting_reactant
#stoichiometric
#mol_ ratio

In a chemical reaction, the reacting materials are often mixed in stoichiometric quantities, according to fixed mole ratios (i.e. in the correct amounts), so that all reactants are used up during the reaction. When reactants are mixed in different mole ratios, only limited amount of product is formed, depending on the amounts of reactants present. The reactant that is consumed first, thus restricting the amount of product, is called the “limiting reactant”.
To better understand the concept of the limiting reactant, let’s look at the reaction studied in this experiment between Na3PO4.12H2O and BaCl2.2H2O. The molecular equation is:

2 Na3PO4.12H2O(aq) + 3 BaCl2.2H2O(aq) Ba3(PO4)2(s) + 6 NaCl(aq) + 30 H2O(l)

The reactants are soluble, as well as NaCl, but Ba3(PO4)2 is insoluble (ppt.). Accordingly, the ionic equation is:
6 Na+(aq) + 2 PO43-(aq) + 24 H2O(l) + 3 Ba2+(aq) + 6 Cl-(aq) + 6 H2O(l) Ba3(PO4)2(s) + 6 Na+(aq) + 6 Cl-(aq) + 30 H2O(l)
Canceling the spectator ions in the reaction (Na+, Cl-) and the water, we get the net ionic equation:
2 PO43-(aq) + 3 Ba2+(aq) Ba3(PO4)2 (s)
Two moles of phosphate ions from 2 moles of Na3PO4.12H2O (M.mass = 380.2 g/mol), react with 3 moles of barium ions from 3 moles of BaCl2.2H2O (M.mass = 244.2 g/mol) producing 1 mole of Ba3(PO4)2 precipitate (M.mass = 602.2 g/mol) if the reaction proceeds to completion.

In this experiment, an unknown salt mixture of Na3PO4.12H2O and BaCl2.2H2O is added to water producing insoluble Ba3(PO4)2. Weighing the initial salt mixture and the product’s final mass, we determine the limiting reactant and the salt mixture’s composition.