Standard Solution (Part A and B)
The purpose of this experiment is to prepare a standard solution of potassium hydrogen phthalate and use titration to perform an acid/base reaction between the potassium hydrogen phthalate and sodium hydroxide to standardize approximately 0.10 M sodium hydroxide solution. To prepare the Potassium Hydrogen phthalate, a 2.00 grams of KHP was measured to an accurate measurement of 1.980 grams. A total of 100 mL of water was mixed with the KHP solution in the volumetric flask to finally prepare an acidic KHP solution. The molar mass of KHP was calculated and came to be 208.252 grams per mole. To find the moles of KHP, the mass of KHP (1.980 g) was divided by the molar mass of KHP ( 208.252 g) and .00951 moles are in the 1.980 grams of KHP. To find the molarity, the number of moles of KHP (.00951 moles) was divided by the volume of water in liters (.100 L) giving an answer of 0.0951 M. The second part of the experiment is the reaction of acid/base through titration. The acid, KHP, was placed in one burette while 100 mL of base, stock solution of NaOH, was placed in another burette. 25 mL of KHP was placed into the Erlenmeyer flask, which was also recorded as the volume of acid in the flask. A total of 19 mL of base, NaOH, was required for the endpoint, which was indicated by a very pale pink color. To calculate the molarity of NaOH, the following equation was used MNaOH x VNaOH = MKHP x VKHP therefore the molarity was .125 M.
This lab experiment covers the preparation of standard solution and the acid/base titration. The first part of the lab is to prepare a standard solution of Potassium hydrogen per. A standard solution is a solution of known concentration, in which it is prepared using exacting techniques to make sure that the molarity is to the highest accuracy. The stock solution on the other hand, which is also a base in this experiment, is a large volume of a common reagent prepared to the 1 or 2 significant figures of accuracy. The stock solution in this experiment is 0.10 M Sodium Hydroxide. Standard solutions are only created when needed and is kept for a short time frame because the common reagents decay over time and collect additional water therefore changing the concentration as a function of time. Once a solution is standardized, this solution is used to quantitatively measure the number of chemicals in other solutions along with the chemicals used to react with the standard solution. The first method, which is used to prepare the potassium hydrogen phthalate, for preparing standard solution is to use solids that have a high stability in air because these can be weighed on a balance without losing or gaining mass. An alternative method is preparing standard solutions to create a solution and than react this solution with a another standard solution. After the standard solution is prepared, part B is to create an acid/base reaction between potassium hydrogen phthalate and sodium hydroxide to standardize the approximately 0.10 M sodium hydroxide stock solution. Sodium Hydroxide cannot be used to prepare a standard solution through the first method because it is hygroscopic and readily absorbs water from air. Sodium hydroxide also reacts with carbon dioxide in air and can’t be stored for long periods of time therefore the stock solution of sodium hydroxide is standardized using the second standardization method. Acid/base reactions are neutralization reactions that create a salt and at times water. The only method to accurately conduct acid/base neutralization reactions is titration. Titration is the precise measurement of volume of one reactant of known molarity required to completely react with another reactant of unknown molarity in a chemical reaction. When a reaction is done, the titration has reached its end point or also known as equivalence point therefore titrations are best used to figure out the accurate concentration...
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