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EXPERIMENT #2: TITRATION OF SODA ASH 2a. Preparation of Approx. 0.1 N HCl … Chem/Images/Exp 2 Soda...
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EXPERIMENT #2: TITRATION OF SODA ASH 2a. Preparation of Approx. 0.1 N HCl Solution Introduce approximately 8 ml of concentrated HCI (12 N) into a one-liter beaker and dilute with distilled water to one liter. Mix thoroughly, then transfer to a stoppered glass bottle and label. 2b. Preparation of Approx. 0.1 N NaOH Solution Boil one liter of distilled water in a large beaker, then remove from heat and allow to cool. On a triple beam balance, weigh out about 4 grams of NaOH pellets. Do not touch these with bare hands! Add the pellets to the beaker of cooled DI water and dissolve thoroughly. When the solution has cooled after mixing, transfer the solution to a polyethylene bottle and label. 2c. Standardization of N~OH Solution with Pure Potassium Acid Phthalate Put the KHP into an unstoppered weighing bottle, and place the bottle into a labeled, covered small beaker. Heat in an oven for one hour, then allow to cool for 20 minutes. Weigh out three portions of 0.7-0.8 grams each into 250 cc Erlenmeyer flasks, recording the actual weights. To each sample add about 50 ml DI water and 3-5 drops phenolphthalein indicator. Rinse a clean buret three times with small portions of the NaOH solution, then fill the buret with NaOH. Make certain the tip is free of air bubbles. Record the initial reading of the buret. Run the NaOH through the buret into the KHP solution slowly while stirring until the solution just turns pink. Proceed dropwise until the entire solution remains pink for longer than three seconds. Stop the titration and record the reading on the buret. Determination of the AcidIBase Ratio Fill one buret with NaOH solution and another buret with HCI solution after cleaning each buret and rinsing three times with its corresponding solution as described above. Again, be sure no air bubbles remain in the tips of the burets. Record the initial readings of each buret. Run out about 20 ml of acid into a 250 cc Erlenmeyer flask, and add 50 ml DI water and 3 drops of bromcresol green indicator. Add base from the other buret, while swirling the flask, until the color of the solution changes from yellow to blue. Rinse the sides df the flask with a small amount of water, then add acid until the solution just turns yellow. In this way, accurately adjust the mixture until a drop of either racid or base will cause a definite change of color. Select the point at which the faintest tinge of yellow appears as the end-point of the titration; later, always titrate to this point. Record the readings of the burets, and calculate the volume ratio.
Transcript of EXPERIMENT #2: TITRATION OF SODA ASH 2a. Preparation of Approx. 0.1 N HCl … Chem/Images/Exp 2 Soda...
EXPERIMENT #2: TITRATION OF SODA ASH
2a. Preparation of Approx. 0.1 N HCl Solution
Introduce approximately 8 ml of concentrated HCI (12 N) into a one-liter beaker and dilute with distilled water to one liter. Mix thoroughly, then transfer to a stoppered glass bottle and label.
2b. Preparation of Approx. 0.1 N NaOH Solution
Boil one liter of distilled water in a large beaker, then remove from heat and allow to cool. On a triple beam balance, weigh out about 4 grams of NaOH pellets. Do not touch these with bare hands! Add the pellets to the beaker of cooled DI water and dissolve thoroughly. When the solution has cooled after mixing, transfer the solution to a polyethylene bottle and label.
2c. Standardization of N ~ O H Solution with Pure Potassium Acid Phthalate
Put the KHP into an unstoppered weighing bottle, and place the bottle into a labeled, covered small beaker. Heat in an oven for one hour, then allow to cool for 20 minutes. Weigh out three portions of 0.7-0.8 grams each into 250 cc Erlenmeyer flasks, recording the actual weights. To each sample add about 50 ml DI water and 3-5 drops phenolphthalein indicator. Rinse a clean buret three times with small portions of the NaOH solution, then fill the buret with NaOH. Make certain the tip is free of air bubbles. Record the initial reading of the buret. Run the NaOH through the buret into the KHP solution slowly while stirring until the solution just turns pink. Proceed dropwise until the entire solution remains pink for longer than three seconds. Stop the titration and record the reading on the buret.
Determination of the AcidIBase Ratio
Fill one buret with NaOH solution and another buret with HCI solution after cleaning each buret and rinsing three times with its corresponding solution as described above. Again, be sure no air bubbles remain in the tips of the burets. Record the initial readings of each buret. Run out about 20 ml of acid into a 250 cc Erlenmeyer flask, and add 50 ml DI water and 3 drops of bromcresol green indicator. Add base from the other buret, while swirling the flask, until the color of the solution changes from yellow to blue. Rinse the sides df the flask with a small amount of water, then add acid until the solution just turns yellow. In this way, accurately adjust the mixture until a drop of either racid or base will cause a definite change of color. Select the point at which the faintest tinge of yellow appears as the end-point of the titration; later, always titrate to this point. Record the readings of the burets, and calculate the volume ratio.
Fill the burets again and repeat the titration. The three ratios should check to within two parts in one thousand.
Exp.;Zc:(d) Standardization of HCI solution aqainst pure sodium carbonate: Dry the salt by placing the unstoppered weighing bottle, properly labeled, into a small beaker and leaving it in the oven at 110°C for one hour. Cool in the desiccator for 20 minutes and weigh out (to nearest 0.1 mg), three portions of 0.4 -0.5 g each, into 250 cc Erlenmeyer flasks, recording the exact weights. Add to each sample about 50 cc of water and 3 drops of bromocresol green solution and shake until dissolved. With both burets full and readings recorded, run in the acid with shaking, until the solution turns yellow. Interrupt the titration, heat the solution to a gentle boil for 2 minutes to expel C02 , and cool the flask contents. If the end point has not been overrun, the indicator will resume its blue color. Wash down the inside of the flask and add acid a drop at a time, until the faintest tinge of yellow returns. (If too much of the acid is added, the excess can be determined by means of the base in the other buret, since the ratio of the solutions is known). After a few moments, read the burets and record the readings. Repeat, using the other carefully weighed portions of sodium carbonate. From the data obtained in each case, calculate the normality factor of the acid, 'and also that of the base, using the average of the triplicate values obtained in determining the ratio of the solutions. The results on the value of the normality factor of both acid and base should agree within two parts in thousand. Save the standardised acid and base for use in other experiments.
2e. Determination of NazCOs in an Impure Sample
Dry the sample in an oven for one hour, and after cooling in a desiccator, accurately weigh out three samples of about 1.0 g each into 250 cc Erlenmeyer flasks. Add 80 ml of water and 5 drops of bromcresol green indicator and swirl. Add HCI solution from buret until the solution just turns yellow. Interrupt the titration, heat the solution to a gentle boil for two minutes to expel Cozy and cool the flask contents. If the end point has not been overrun, the indicator will reassume its blue color. Wash down the inside of the flask and add acid, a drop at a time, until the faintest tinge of yellow returns. Repeat, using the other samples. Calculate the percentage of sodium carbonate in the unknown.
