Gravimetric Analysis of a Chloride Salt

Gravimetric Analysis of a Chloride SaltRania WilliamsNour WehbePurposeTo discover the amount of chloride in a contrary salt, in order to demonstrate regular methods apply in gravimetric analysisTheoryThis equation describes the reaction between silver grey ion and chloride which outgrowths in the product silver chloride.Ag+ (aq) + Cl (aq) AgCl (s)Silver nitrate is used to come chloride because it gives the best results.AgCl Solubility in wetSilver chlorides solubility is very low tho the salt is still dissoluble to almost degree. If precipitate is not complete, the results will be very low.Ksp = 1.6 x 10-10Precipitation come upon outs in red-hot to greatly reduce every interference from pungent ions. These ions form co-precipitates with silver in acid containing no supercharged ions. Due to co-precipitates the results would be higher. Also in order for heedlessness to occur in acid there needs to be some overplus of silver ion at the end of the reaction to reduce the chances of silver chloride comely more soluble. Co-precipitation would result in higher results.Description The precipitate is heat in order to coagulate it. When it coagulates it will become a clumpy colloidal like form. In this form it will become more knotty for the precipitate to penetrate the filter paper. If the coagulate did go through, the results would be visit. If nitrous acid had not been added to the precipitate it would become more vulnerable in penetrating the filter paper. If this had happened the experiment would have to be done once more as there would be no way to determine the ploughshare of chloride in the salt.PhotodecompositionThe equation for photodecomposition occurring in the airAgCl (s) Ag (s) + Cl2(g)When the silver chloride has arid and put into light it will decompose into chlorine and silver. If photodecomposition occurs in air, the results would be low, however if this decomposition occurred with excess silver ion in an aqueous dissolvent there will be another reaction (3Cl2(g) + 9H2O (l) + 5Ag+ (aq) 5AgCl (s) + ClO3(aq) + 6H3O+ (l)), which will make the results high.How much precipitate is incapacitated by washout with 100ml fresh water?Ksp = AgClx x = x21.6 x 10-10 = 1.3 x 10-51.3 x 10-5= C/0.10 LC =1.3 x 10-5x 143 mol/0.10 L C = 0.01859 mol/L(0.01859)(0.10) = 0.001859= 1.810-3 gThe precipitate is unconnected callable to the solubility of it. The solubility of the precipitate is very low so not much would be lost, however this still would make the results lower.Ions that may co-precipitate with chloride ionWhen precipitation occurs quickly the chances of co-precipitation occurring greatly increases. Anions from some acids may co-precipitate with the chloride ion, forming co precipitates. These co precipitates will alter the results, making them CO32-, OH and NO3 subprogramThe code number of the unknown salt that was displace on the pose was recorded. This test was kept for the full duration of the experimen t. Using the analytical balance, 0.1175g of the take was weighed out by difference and placed in a 250ml beaker. The beaker was labeled to avoid confusion between partners.The estimate volume of 0.1 M silver nitrate was calculated using the haves mass, 0.1175g. The mass of the ideal was multiplied by the percentage concentration of the chloride then divided by 35.5. The result was then divided by 0.1. The result was converted into ml. 5 ml of excess was then added to the result, making the final result and approximate volume of silver nitrate added, 23ml.In the 250ml beaker with the sample, 100ml of distilled water and 1ml of 6M nitrous acid was added to the beaker. 23ml of 0.1M silver nitrate was measured out in a 25ml graduate cylinder then slowly poured into the 250ml beaker. The solution was placed on a hot plate then gently stirred. The solution was stirred until it became coda to boiling.In order to test for completeness the solution had a couple drops of silver nitrat e poured into it to test that the entire chloride ion had been precipitated. The solution showed that it was complete. The 250ml beaker with the solution was then placed into the assigned drawer, to limit its light exposure.Using a piece of around the bend tissue paper the melting pot which had already modifyed was weighed, it had a mass of 30.6707. The pointlessness filtration arrangement was set up. The solution without the precipitate was slowly poured into the filter. 5ml of 0.1M azotic acid was used for washing the precipitate. After a couple washings the precipitate was too placed into the filter. A wash bottle was used to help any remaining precipitate out of the beaker. The precipitate was again washed with 0.1M nitric acid.The crucible was then removed from the vacuum filtration arrangement. The leftover washings were disposed of. The crucible was washed once again in the vacuum filtration arrangement. The washing (mainly nitric acid) was taken to the T.A. for testin g if the precipitation is complete by doing a washing with hydrogen chloride on the nitric acid. The first test showed completeness.The crucible was again latched onto the vacuum filtration arrangement to be washed with 3ml of acetone. The acetone was handed to the T.A. for disposal. The crucible was given to the T.A. to put in the oven for drying of the precipitate. The oven had a starting temperature of 110 C and after 30 minutes had a temperature of 119 C.The crucible was then cooled in the desiccator for 10 minutes then weighed with an analytical balance. The result was recorded.ObservationsData tables seek massesCrucible massesApproximate volume of the liquids and solutions used to was the sampleTemperature of OvenCrucible drying and cooling timesCalculationsAmount of AgNO3 required (calculated amount + 5mL)(0.1175)(0.55)/35.5/0.10.018204225 * 1000mL/1L = 18.20422518.204225 + 5 = 23.20422525mL23mL of AgNo3 neededPercentage chloride in sampleUncertainties congress errorRelative spread of the percentage of chloride found62.06% 56.92% / 59.49%= 0.086401076 * 10= 0.86401076 ppt= 0.8640 pptDiscussionMy results were higher callable to the photodecomposition of the precipitate that most likely occurred due to an excess of silver ion in the solution. This was a result of human error, as I waited for the precipitate to cool down I did not leave it out of light and failed to discipline that there was not an excess of silver ion in my solution. My results could similarly be higher due to any co-precipitates from anions such as these CO32-, OH and NO3 . The results could have also become higher due to not being washed properly. When washing the precipitate only with 3ml of acetone and 5ml of water this may have been possible. When compared with the certain result, my result was higher.My partners results were lower than the real value due to some of her sample being lost during filtration. Sample being lost during filtration is almost unavoidable. Even though s he may not have lost a lot of her sample, her initial salt mass was just 1.002g. Losing sample from a sample that was already so small contri moreovered to her results being lower than the real(a) value. She also may have not allowed for complete precipitation of the chloride ion, resulting in lower results. During the heating of her solution her precipitate coagulated but there were stills some parts of the precipitate that were very tiny were susceptible of being loss the vacuum filtration. When compared with the actual result, my partners result was lower.The average of my partner and Is results were very close to the actual result, though the average of our results was still higher than the actual result.ConclusionThe sample number for the unknown salt is 343. The average percentage of the chloride from two trials is 59.49%, whilst the actual percentage of chloride is 58.81%. The uncertainty for the percentage of chloride for my results was 0.2041 and 0.2430 for my partner. The precision of my results was 5.526%, whilst my partners was 3.214%. The accuracy of the results was 0.8640 ppt.ReferencesBooksR.C.Burk, M.Azad, X.Sun, P.A. Wolff, Introductory Chemistry Laboratory Manual, Carleton University, Ottawa, 2014-15.WebsitesBishop, Mark. Bases. Bases. CHIRAL PUBLISHING COMPANY. 2013. Web. http//preparatorychemistry.com/Bishop_Base_Identification.htm.