Exp 1: Preparation & Standardization of 1N HCl PDF

Pharmaceutical Analysis 1 - Laboratory 1st Semester Prelims | Prof. Renato I. Dalmacio, RPh., MSPharm. ____________________________________________________________________________________________________________________________________ Exp 1: Preparation & Standardization of...

Pharmaceutical Analysis 1 - Laboratory 1st Semester Prelims | Prof. Renato I. Dalmacio, RPh., MSPharm. ____________________________________________________________________________________________________________________________________ Exp 1: Preparation & Standardization of II. Standardization of 1N Hydrochloric Acid Solution 1. Weigh accurately 150 mg of anhydrous Sodium 1N HCl carbonate that was previously heated at ______________________________ temperature of 270° C for 1 hour. 2. Dissolve the sodium carbonate in 100 mL of At the end of the experiment, the student should be able to: distilled water. To prepare and standardize 1 normal hydrochloric 3. Add 2 drops of sa methyl orange TS. acid solution. 4. Titrate with Hydrochloric acid solution until color To apply the principle involved in the preparation changes from yellow to orange. and standardization of 1 normal hydrochloric acid 5. Each 52.99 mg of anhydrous sodium carbonate is solution. equivalent to 1 mL of 1N Hydrochloric acid. 6. Determine the normality of Hydrochloric acid solution. OVERVIEW 7. Repeat the procedure and perform 3 trials. Hydrochloric acid is produced in solutions up to 38% HCl (concentrated grade). Higher concentrations up to just over 40% are chemically possible, but the evaporation rate is then so high that storage and handling need extra precautions, such as pressure and low temperature. Laboratory grade hydrochloric acid is not sufficiently pure to be used as a primary standard, because it evaporates easily. In this experiment, a standard solution of sodium carbonate is used to determine the exact concentration of a hydrochloric acid solution. COMPUTATION Normality = gm/mEq x mL The neutralization reaction that occurs is as follows: 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑛ℎ𝑦𝑑𝑟𝑜𝑢𝑠 𝑆𝑜𝑑𝑖𝑢𝑚 𝐶𝑎𝑟𝑏𝑜𝑛𝑎𝑡𝑒 (𝑔𝑟𝑎𝑚𝑠) 𝑁= (105.99/2000) · 𝑚𝑙 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑖𝑛 𝐻𝐶𝑙 𝑠𝑜𝑙'𝑛 Procedures DATA I. Preparing of 1N Hydrochloric Acid Solution 1. Pour around 200 mL of distilled water into a 1 L volumetric flask. 2. Add 85 mL of Hydrochloric acid cautiously and gradually shake after addition. 3. Add enough distilled water to complete the volume to 1 L. 4. Pour the Hydrochloric acid solution into 1 L stock bottle. 5. Label properly. Exp 2: Preparation & Standardization of Standardization 0.1N NaOH Solution ______________________________ It is the process of determining the exact concentration of a solution. At the end of the experiment, the student should be able to: It is an analytical technique we use to find an Demonstrate the laboratory procedures involved in unknown concentration using a primary the preparation and standardization of 0.1 N (chemically pure solid, 99%) or a secondary (not sodium hydroxide solution. necessarily pure but the concentration is known) Apply the principle in calculation of normality of standards prepared volumetric solution. Procedures Volumetric Analysis I. Preparing of 0.1 N Sodium Hydroxide Solution Volumetric analysis is a chemical analytical 1. Weigh 4.5 grams of sodium hydroxide pellets in a procedure based on measurement of volumes of beaker. reaction in solutions. It uses titration to determine 2. Dissolve in small portions of carbon dioxide free the concentration of a solution by carefully water. measuring the volume of one solution needed to 3. Allow the solution to cool to room temperature. react with another. In this process, a measured 4. Transfer the solution into 1 liter volumetric flask volume of a standard solution, the titrant, is added and dilute it to volume with carbon dioxide free from a burette to the solution of unknown water. concentration. 5. Store the solution in a 1 L stock bottle. 6. Label the solution properly. Acid-Base Titration II. Standardization of 0.1N Sodium Hydroxide Solution 1. Weigh accurately 100 mg of potassium biphthalate, It is the process whereby an amount of an acid has previously dried at 120 C for 2 hours. reacted with an equivalent amount of a base with 2. Dissolve in 75 mL carbon-dioxide free water. the production of SALT and WATER. 3. Add 2 drops of phenolphthalein TS. Neutralization Reaction 4. Titrate with the prepared NaOH solution to the The principle involved in volumetric method. production of a permanent pink color. Each mL of 0.1 N NaOH is equivalent to 204.23 mg of IMPORTANT TERMS potassium biphthalate. Titrant - the substance in the burette, the one 5. Determine the normality of the solution. being determined Analyte - titrand, substance that is 99% pure Indicator - any chemical capable of changing color COMPUTATION: to determine endpoint Normality = gm/mEq x mL End point - stage at which the reaction is complete, often indicated by a color change 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑃𝑜𝑡𝑎𝑠𝑠𝑖𝑢𝑚 𝐵𝑖𝑝ℎ𝑡ℎ𝑎𝑙𝑎𝑡𝑒 (𝑔𝑟𝑎𝑚𝑠) Equivalence Point - when the amount of titrant 𝑁= (204.23/1000) · 𝑚𝑙 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑖𝑛 𝑁𝑎𝑂𝐻 𝑠𝑜𝑙'𝑛 added is enough to react with the analyte, stoichiometric point *Express in 4 decimal places DATA & RESULTS: Exp 3: Assay of Sodium Bicarbonate Tablets ______________________________ COMPUTATION: At the end of the experiment, the student should be able to: 𝑚𝐿 × 𝑁 𝐻𝐶𝑙 × 𝑚𝐸𝑞 (84.01/1000) To determine the purity or % label claim of sodium % 𝐴𝑠𝑠𝑎𝑦 = 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑆𝑎𝑚𝑝𝑙𝑒 (𝐺𝑟𝑎𝑚𝑠) × 100 bicarbonate in sodium bicarbonate tablets using direct titration. To apply the principle involved in the assay of Specification: USP requires Sodium Bicarbonate tablets to sodium bicarbonate tablets. contain not less than 95.0% and not more than 105.0% of NaHCO3. OVERVIEW DATA & RESULTS Combining an acid with a base typically results in water and salt. In some cases, these reactions release gas and heat as well. Alka Seltzer® is an over-the-counter antacid and pain relief medication that is taken by dissolving it in water before ingesting. The effervescent tablet contains aspirin, citric acid, and NaHCO3. As soon as the tablet dissolves in water, an acid-base reaction involving the sodium bicarbonate takes place. Baking soda mainly contains sodium bicarbonate. When this is treated with dilute hydrochloric acid, the following reaction occurs: NaHCO3 + HCl → NaCl + ↑CO2 + H2O Alkalimetry - titration used to determine the concentration of an acidic substance by titrating it with a standard alkaline (basic) solution Acidimetry - assay of NaHCO3, titration used to determine the concentration of a basic (alkaline) substance by titrating it with a standard acidic solution PROCEDURE Assay of Sodium Bicarbonate Tablets 1. Weigh and finely powder not less than 20 Tablets. 2. Weigh accurately a portion of the powder, equivalent to about 2 g of sodium bicarbonate, dissolve in 100 mL of water, add methyl red TS, and titrate with 1 N hydrochloric acid VS. 3. Add the acid slowly, with constant stirring, until the solution becomes faintly pink. Heat the solution to boiling, cool, and continue the titration until the pink color no longer fades after boiling. 4. Each mL of 1 N hydrochloric acid is equivalent to 84.01 mg of NaHCO3. 5. Calculate the amount of sodium bicarbonate. 6. Repeat the procedure and perform 3 trials. Exp 4: Preparation and Standardization II. Standardization of 0.1 N Sulfuric Acid Solution of 0.1N Sulfuric Acid Solution 1. Run out 20 mL of 0.1 normal sodium hydroxide ______________________________ solution into a clean and dried Erlenmeyer flask. 2. Add 2 drops of methyl orange TS. At the end of the experiment, the student should be able to: 3. Titrate with sulfuric acid solution from yellow color to orange color endpoint To prepare and standardize 0.1 normal sulfuric acid 4. Determine the normality of Sulfuric acid solution. solution. 5. Repeat the procedure and perform 3 trials. To apply the principle involved in the preparation and standardization of 0.1 normal sulfuric acid solution. OVERVIEW Sulfuric acid is a diprotic acid and 1 N solution contains 98.08/2 = 49.04 g H2SO4. Taking into consideration specific gravity (1.83) of sulfuric acid about 49.0 ml of conc. Sulfuric acid is required to prepare a 1000 ml solution. It is an example of alkalimetry. When a strong acid is titrated with a strong base, the salt produced in the reaction is not hydrolyzed and therefore the pH of the resultant solution at the end point is exactly 7.0. The standardization of sulfuric acid solution can also be effected by titration against normal sodium COMPUTATION: hydroxide solution using phenolphthalein as an indicator. The reaction between sulfuric acid and 𝑚𝐿 𝑥 𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑡𝑦 𝑜𝑓 𝑆𝑜𝑑𝑖𝑢𝑚 𝐻𝑦𝑑𝑟𝑜𝑥𝑖𝑑𝑒 𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑁= 𝑚𝐿 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑏𝑦 0.1 𝑆𝑢𝑙𝑓𝑢𝑟𝑖𝑐 𝑎𝑐𝑖𝑑 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 sodium hydroxide is called neutralization, and the products are sodium sulfate and water only. *express in 4 decimal places The molecular equation is: DATA & RESULTS Procedures I. Preparing of 0.1 N Sulfuric Acid Solution 1. Add slowly, with stirring 3.0 mL of concentrated sulfuric acid to 120 mL of distilled water. Allow to cool to 25 ° C. 2. Pour the sulfuric acid solution into a 1 L volumetric flask. 3. Rinse the beaker with distilled water and pour the rinsing into the 1 L volumetric flask. 4. Add enough distilled water to complete the volume to 1 L. 5. Store the solution in a 1 L stock bottle. 6. Label properly.