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Unformatted text preview: Identification and Properties of Unknown Acids Abstract This paper describes the identification, properties, and proper disposal of four unknown acids. The acids were identified with overwhelming certainty by the calculation their densities, the use of anion tests, and determination of molarity. The relationship between molarity and pH was also investigated. To determine the densities of the four unknown acids, 5 mL of each acid was weighed and density of the acid was determined through the density formula (d = m/v). The experimental values that were determined for the densities were 1.18 g/mL (hydrochloric acid), 1.39 g/mL (nitric acid), 1.69 g/mL (phosphoric acid), and 1.78 g/mL (sulfuric acid). These experimentally determined densities were very close to the reported values on the acid bottles. Anion tests were then performed to confirm the identity of these acids. As expected, hydrochloric acid was positive for the chloride anion, nitric acid was positive for the nitrate anion, phosphoric acid was positive for the phosphate anion, and sulfuric acid was positive for the sulfate anion. The molarities of the acids were then investigated using titration. The experimental values calculated from this process were 9.62 mol/L (hydrochloric acid), 14.5 mol/L (nitric acid), 13.38 mol/L (phosphoric acid), 17.16 mol/L (sulfuric acid). These experimental molarities were then found to be very close to the reported molarities found on the stock bottles of acid. Finally, a titration curve was created from the acid/base titration of phosphoric acid and sodium hydroxide. The equivalence points of the graph proved to be when the molarity of the acid and the base were equal. Therefore, it was seen that through the property tests there was an overwhelming certainty of the identification of the acids. The acids were then disposed of according to the proper regulations of the lab we were in. Introduction The goals of this project were to identify the unknown acids through the investigation of the properties and determine the proper methods of disposal. First, the densities of the acids were determined by using a known volume, weighing it on an analytical balance, and using the density formula (d = m/v) to determine its density. Anion tests were then performed to further verify the identity of the unknown acids. The chloride, nitrate, phosphate, and sulfate anion tests were used to verify the presence of these anions in the acids that were under investigation. Molarity, or concentration, of the acids was then determined through the acid/base titration. Before the titration could be performed the sodium hydroxide base needed to be standardized because of the variance of molarity from the stock solution. By using sodium hydroxide as a base of known molarity and finding the volume to titrate the same number of moles of the acid, the molarity of the acid was able to be determined by using reaction stoichiometry. Phenolphthalein was used as the acid/base indicator in the experiment to indicate the end point of the titration, or the point at...
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This note was uploaded on 02/25/2012 for the course CHEM 2142 taught by Professor Roberts during the Fall '10 term at Texas State.
- Fall '10