Limiting Reactants Essay

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Limiting Reactant Lab Rona Hunter August 31, 2011 Purpose: The purpose of this lab is to determine the limiting reactant in a salt mixture, and to determine the percent composition of each substance in a salt mixture, therefore increasing our understanding of the concepts of limiting reactants, percent composition, and laboratory techniques of heating and filtering precipitates. Procedure: Weigh two samples of about 1.0 g of the salt mixture in separate beakers. Add about 200 mL distilled water, stir, and allow precipitate to settle. Heat the solutions on a hot plate while covered with a watch glass, at 80-90 degrees Celsius for 30 minutes. Allow the precipitate to settle, and heat 30 mL distilled water. Weigh, fold and place two filter papers into funnels and seal with distilled water. Decant a 50 mL sample from each beaker of solution into two other beakers. Pour the rest of the solutions into the respective funnel filters, and make sure to wash all precipitate into the filter, using the heated distilled water. Remove and air dry the filter papers containing the precipitates. Add two drops of 0.5 M Ba2+ to the 50mL sample of the first supernatant liquid, and observe. Add two drops 0.5 M PO4 3- to the 50mL sample of the second supernatant liquid, and observe. Dispose of waste properly. Theory: One of the chemical principles being utilized in this experiment is the principle of limiting reactant. Every chemical reaction can only continue for as long as the amounts of reactants are not used up. Whichever reactant’s amount is used up first, causing the reaction to halt and therefore determining the amount of product is called the limiting reactant. Another factor that limits the amount of product yield is the percent yield of the reaction, meaning how much product can be created based on the mole ratios between the reactants and the products.

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