Chem lab # 5

Adam McGowan X03506367 Molecular Mass of an Acid and the analysis of Vinegar Monday 10/27/18 3:40-7:00

Standardization of sodium hydroxide solution Data Mass of KHP .350g .335g .315g Initial Buret reading 0ml 0ml 0ml Final Buret reading 17ml 26ml 18ml Volume of NaOH solution used 17mol 26mol 18ml Molarity of NaOH 1.01E-4M 9.65E-4 9.07E-5 Average Molarity of NaOH: 2.880E-4M Uncertainty of NaOH : .00300M Molecular mass of an unknown monoprotic acid: sample #902 Data Mass of unknown acid .262g .232g .296g Initial Buret reading 0ml 0ml 0ml Final Buret reading 19ml 20.2ml 21.67ml Volume of NaOH solution used 19mol 20.2mol 21.67ml Results Moles of NaOH used .0059mol .0075mol .0052mol Moles of acid reacted .0059mol .0075mol .0052mol Molecular mass of acid 44.41g/mol 30.93g/mol 21.67ml Average Molecular mass of acid: 44.087g/mol Uncertainty molecular mass acid :.00390g/mol Trail 3 Trail 2 Trail 1 Trail 3 Trail 2 Trail 1 Trail 3 Trail 2 Trail 1

Questions 1. The students do three replicate titrations to eliminate any chance for error. The students would do the titrations three times and get the average of the three times. This average would be more accurate and would have little human error. 2. Titrations of the acid-base function can be done on almost any type of acidic and basic acids, such as finding the concentration of NaOH in drain cleaner, or the concentration of HCI in pool acid. Another common household item that can be analyzed by titrations is the concentration of H2SO4 in battery acid. 3. It is important to add indicator because the indicator is what gives a visible sign (usually by color change) of the appearance of reaching the upper limit of concentration. If a solution has no indicator in it, the researchers will be unable to determine the limit of the concentration in the solution. 4. Weighing by difference is a method of measurement used to measure quantitatively the mass of a solid sample. This is done through various weightings of the reagent and finding the difference in the two masses; the reagents and the vessel. This technique is used many times in this experiment, including when getting samples of substance in flasks and containers, and subtracting the mass of the container or flask to get the mass of the actual sample.