Introduction Soda ash or sodium carbonate is a commonly used neutralizing agent such as in eliminating corrosion and to control pH in water treatment It is also an essential raw material in glass detergents and other industrial products Like most chemical substances soda ash is usually not found in its pure form sodium carbonate or Na2CO3 as it tends to also have small amounts of NaOH and NaHCO3 present 1 For this reason determining the total amount of sodium carbonate in solution requires a specific procedure A major aspect of analytical chemistry is being able to find the concentration of an unknown sample There are various ways of doing so including chromatography spectrometry absorption pH or titrations For this lab titrations are performed in order to find the concentration of the unknown samples The purpose of a titration is to use a known concentration of a substance in order to find the equivalence point of a known or unknown analyte thus being able to find its concentration As the unknown sample in this experiment is soda ash a titration must be prepared appropriately for the analyte Because soda ash is a weak base it would prove beneficial to use a strong acid as the titrant such as HCl as a strong acid and weak base react well Along with a good titrant a proper indicator with the correct pH range must be chosen Sodium bicarbonate coupled with a strong acid such as HCl has two equivalence points the first being the conversion to bicarbonate and the second to carbonic acid 2 The first equivalence point occurs at a pH of about 8 0 and the second at a pH of about 4 0 making phenolphthalein and screened methyl orange good indicators for the two reactions respectively 1 Determination of the Carbonate Content of a Soda Ash Sample https chem libretexts org go page 75254 accessed Sep 29 2021 2 Jacobs A Neutralization Titrations Determination of Soda Ash University of Florida Department of Chemistry Gainesville FL 2019 Calculations 6 Titration of KHP with NaOH Moles of KHP in solution Moles mol Grams KHP 1 mol KHP 204 22 g 1 0 0946 g 0 00046 mol 2 0 1071 g 0 00052 mol 3 0 1068 g 0 00052 mol Molarity of NaOH M of NaOH 1mol NaOH 1 mol KHP 1 1 L of NaOH added 1 9 40 mL added 0 049 M 2 10 455 mL added 0 050 M 3 9 70 mL added 0 054 M Average M of NaOH 0 051 M NaOH M 1 M 2 M 3 3 SD of NaOH s x x 2 n 0 003 RSD of NaOH CV 0 05 s x Titration of HCl with 0 051 M NaOH Moles of NaOH 0 051 L of NaOH added mol L Trial 1 9 4 mL NaOH added 0 00048 mol NaOH Trial 2 10 455 mL NaOH added 0 00053 mol NaOH Trial 3 9 70 mL NaOH added 0 00049 mol NaOH Molarity of HCL 1 0 00048 mol NaOH 0 096 M HCl 2 0 00053 mol NaOH 0 11 M HCl 3 0 00049 mol NaOH 0 099 M HCl Average 0 10 M HCl Standard Deviation 0 0007 Relative standard deviation 0 007 M of HCl X mol NaOH x 1 mol HCl 1mol NaoH 1 0 005 L HCl stock soln 0 1 mol HCl 1 L of HCl 1 mol of Na2C O3 2 mol of HCl 106 g 1 mol Na2C O3 0 025 g of Na2C O3 0 00503 L of HCl 0 1 mol HCl 1 L of HCl 1 mol of Na2C O3 2 mol of HCl 106 g 1 mol Na2C O3 0 027 g of Na2C O3 0 1 mol HCl 1 L of HCl 1 mol of Na2C O3 2 mol of HCl 106 g 1 mol Na2C O3 0 027 g of Na2C O3 Average by weight 1 2 3 3 33 30 w w Soda Ash calculations Sample 38 weight g of solute g of sample x100 1 0 0733 g of soda ash 0 00475 L of HCl w w 34 35 w w 2 0 0875 g of soda ash w w 30 47 w w 3 0 0756 g of soda ash 0 005005 L of HCl w w 35 09 w w s x x 2 n 2 RSD CV 0 07 s x Questions 1 The required properties of a primary standard solid are that they have high purity a reasonable cost thermal stability chemical stability known chemistry and a high equivalence weight NaOH is not a primary standard because it is hygroscopic meaning that it attracts moisture from the air so the concentration varies over time suggesting that the actual concentration of NaOH will be lower than the anticipated theoretical concentration 2 A standard solution is a solution of known concentration to at least 4 significant figures The two methods of preparation depend on if the required compound is in primary standard grade or not If it is a primary standard one must first weigh the solid and dissolve it into a small amount of water in a beaker Then this should be properly transferred to a volumetric flask utilizing a funnel and stirring rod as well as rinsing the rod and beaker multiple times and dispensing these rinsings into the volumetric flask Finally one must dilute the solution to the desired volume and mix thoroughly It must be stored properly The second method of preparing a standard solution involves using a non primary standard grade solid In this case a solution is prepared with approximately the desired concentration Then an analytical method is used such as a titration using a primary standard solid that reacts with the substance This is known as a standardization titration The two standard solutions were prepared using method 2 NaOH concentration was determined through titration with a primary standard solid KHP HCl was determined with the titration with standardized NaOH 3 Because NaOH is hygroscopic it absorbs both moisture and CO2 from the air If CO2 is absorbed it will form Na2CO3 This carbonate ion can interfere with the titration as it will affect the standard concentrations and the acid base reaction that is supposed to occur By preparing sodium hydroxide in a diluted solution one can avoid the solid state of NaOH that would react with CO2 4 HCl aq NaOH aq H2O l NaCl aq Net ionic H aq OH aq H2O l NaOH aq KHC8H4O4 aq H2O l KNaC8H4O4 aq Net ionic H aq OH aq H2O l Na2CO3 aq 2HCl aq 2NaCl aq H2O l CO2 g Net ionic CO3 2 aq 2H aq H2O l CO2 g 5 2NaHCO3 aq Na2CO3 s H2O g CO2 g Net ionic 2 HCO3 aq CO3 2 aq H2O l CO2 g