Formal Lab 1 - Stoichiometric Reactions with Phosphoric...

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Stoichiometric Reactions with Phosphoric Acid CHE 120 - 03 March 2, 2008 Purpose In this exercise you will perform three acid/base neutralization reactions of a triprotic acid, phosphoric acid, with varying molar equivalents of sodium hydroxide in order to examine the stoichiometric relationship between the
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reagents and the identity of the products formed. Experimental data will be used to determine the formula weight of the products and the identity of the resulting salt of phosphoric acid. Introduction The mole (mol) is one of the most important units of measurement in chemistry. The mole describes how man molecules of a substance are required in a balanced chemical reaction. The number of moles required is in direct correlation to the coefficient of the chemical reaction. The use of stoichiometric calculations in relation to the mass of a compound will produce the number of moles needed. Stoichiometry is the part of chemistry that encompasses mass relations in given equations(1). An empirical or molecular formula will tell the relation between moles and mass of a given compound, therefore one atomic mass unit (amu) is equal to one gram/mole. One mole of a substance has a mass in grams that is exactly equal to that same substance’s formula mass (2). Calculating the formula mass of an equation will also give the value of the mass of one mole of a given equation. The molarity (M) of a solution is obtained by dividing the moles of a solute by the liters of solution. For example, 3.00mL of a 5.00 (M) solution would represent 3.00 x .001L x5.00 mol/L or 0.018 mol of solute. A polyprotic acid is a substance that is capable of supplying more than one equivalent of H+ in aqueous solution and therefore is capable of reacting with one or more molar equivalents of sodium hydroxide in a neutralization reaction. When reacting an acid with multiple molar equivalents of a base the compound produced from the neutralization can differ based on the molar equivalent. The difference between the equations can be expressed by NaH(CO)3 vs. Na(CO)3. This experiment will determine the mass of salt formed in three reactions between phosphoric acid and a molar equivalent of sodium hydroxide. The mixture will be heated until the excess water has evaporated out and only the salt remains. Based on the mass of the salt the formula weight, empirical formula, and name of salt can be attained. It is important to maintain the stoichiometry of the reactions in order to maintain accurate results throughout the experiment. The moles of each reagent can be achieved by multiplying the molarity by the
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This note was uploaded on 04/18/2008 for the course CHE 120 taught by Professor Saroj during the Spring '08 term at S. Connecticut.

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Formal Lab 1 - Stoichiometric Reactions with Phosphoric...

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