The percent yield is a measure of the efficiency of the reaction in producing products. By both calculating the amount of CaCO 3 that forms and measuring it in the lab it will be possible to calculate the percent yield for the reaction. This lab is designed to provide data which demonstrate the validity of the mathematical techniques of stoichiometry. The amount that forms is determined by the molar ratio between these two chemicals as seen in the chemical equation given above. In the reaction carried out in this lab the CaCO 3 forms by the chemical reaction of sodium carbonate with calcium chloride. It is also the primary component of the shells of marine mollusks and is a very common source of calcium in calcium supplement pills. This substance is familiarly known as chalk, limestone, or marble. This makes the Na 2CO 3 the limiting reagent and the amount of calcium carbonate ( CaCO 3) produced will depend only on how much Na 2CO 3 is present.Ĭalcium carbonate has very low solubility in water and is usually considered completely insoluble. This amount of CaCl 2 is in stoichiometric excess over the Na 2CO 3 that will be used. This volume contains 0.060 L × 1.0 mol/1 L = 0.060 mol CaCl 2. In this procedure a volume of 60 mL of this solution is used. The calcium chloride solution has a concentration of 1.0 mol/L (usually written 1.0 M). Next, a solution of calcium chloride ( CaCl 2) is mixed with the solution of Na 2CO 3. Using distilled water reduces the chance that any excess carbonate ions may be present. In this lab a sample of sodium carbonate ( Na 2CO 3) with a mass of 4 - 5 g is dissolved in distilled water. Stoichiometry is the technique of using the molar ratios in balanced chemical equations to calculate the amount of reactants or products. The mass of calcium carbonate will then be compared with the mass predicted by stoichiometric calculations. The solid precipitate will be collected, dried and weighed. Precipitates form due to their low solubility in water. A precipitate is a solid compound that results from the reaction of two soluble compounds in a solution. These notations are included to show that a precipitate forms in the reaction. In the chemical equation above the notation ( aq) means ‘aqueous’, that is, dissolved in water.
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