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Unformatted text preview: Purpose : To determine the percentage of NaHCO 3 in a sample of baking soda from the Athenium Baking Soda Company. We must also identify any impurities in the sample in the form of lithium, potassium, or calcium. Background : Baking Soda can be used for an array of jobs. We use it for cleaners, baking, toothpaste, and odor eliminators; therefore, Baking Soda, NaHCO 3 must be pure to be effective and safe for our use. The Athenium Baking Soda Company created an amount of Baking Soda contaminated with chemicals, which was used to test chemists applying for a job at the company. The Chemistry 1211 students are to complete a similar simulated experiment to find the concentration and composition of a Baking Soda mixture given to them. The quality control scientists must use the most accurate analysis techniques which include Emission, Titration and Thermal Gravimetric analysis. By using the Emission analysis, the presence of Group 1 and Group 2 metal ions can be determined. The students will use the known solutions of Calcium Chloride, Potassium chloride, and Lithium Chloride to find the approximate wavelength versus intensity for each metal ion so that we can perform the emission analysis on the baking soda mixture and know if those ions are present in the mixture. The students will use Titration analysis to determine the concentration of NaHCO 3 in the Baking Soda Mixture by slowly adding HCl to the solution until an equivalence point can be determined. The equivalence point is the point that the acid and base are completely neutralized and can be detected by a sharp decrease in pH. pH is the negative of the logarithm of the hydrogen ion concentration. pH = - log (H 3 + ) (equation 1) The equation: Na 2 CO 3 + 2HCl -> 2NaCl + H 2 O + CO 2 (equation 2) Can be used to determine the concentration of HCl is required to standardize the Na 2 CO 3 . Once the concentration of HCl is known another titration can be performed upon the baking soda mixture to determine the concentration of NaHCO 3 based upon the equation: NaHCO 3 + HCl -> H 2 O + CO 2 (equation 3) When the standardization of Na 2 CO 3 with HCl, two equivalence points will appear which signify different mol ratios of HCl to Na 2 CO 3. When the molarity of the HCl needed is found, students can find the amount of HCl needed to titrate NaHCO 3. Molarity can be found by: Molarity (M) = (moles of solute) / (liter of solution) Thermal Gravitation Analysis will be used to find the percent by mass of the NaHCO 3 in the Baking soda mixture. When NaHCO 3 is heated, it follows the equation: 2NaHCO 3(s)-> Na 2 CO 3(s) + CO 2(g) + H 2 O (g) (equation 4) According to this equation, 2 mols of NaHCO 3 decompose when heated into 1 mol of Na 2 CO 3, CO 2, and H 2 O. Once heating the mixture students can measure the residue and find the percent by mass of the NaHCO 3 by dividing the amount of NaHCO 3 by the total amount of baking soda powder used in the experiment. The percent by mass is the grams of the solute per grams of solution multiplied by 100%.of the solute per grams of solution multiplied by 100%....
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- Spring '08
- sodium bicarbonate, NaHCO3