Solution Preparation and Standardization

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EXPERIMENT 2: SOLUTION PREPARATION AND STANDARDIZATION
Submitted by Iris Olaso
______________________________________________________________________________ INTRODUCTION

Generally, there are two ways in preparing a solution, one is by dissolving a weighed amount of solid in a required solvent and the other is by dilution of a concentrated solution into the desired concentration.

In diluting concentrated solution, the concentration of the diluted solution can be determined by standardization. To standardize a solution, we will need to perform titration. In this experiment, we will standardize acid and base solutions.

In this experiment, the students to students will be able to know the proper way of preparing solutions from solid and liquid reagents by using the proper pieces of glassware and equipment and to calculate the exact concentration of the prepared solution from standardization.

PROCEDURE

The reagents that were used in this experiment were concentrated hydrochloric acid, sodium hyrdoxide, sodium carbonate, potassium acid phthalate and phenolphthalein as indicator.

The pieces of glassware that were used to perform this experiment were volumetric flasks, Erlenmeyer flasks, beakers, volumetric pipette, burette, spatula and droppers. Also, the pieces of equipment that were used were analytical balance, top-loading balance and hot plate.

Preparation of 250 mL 1.0 M sodium hydroxide solution (from solid)

The amount of NaOH needed to prepare 1.0M solution was calculated (10.0 g NaOH). The computed value was weighed using the top-loading balance and placed in a clean and dry 250-mL beaker. Enough amount of distilled water to dissolve the NaOH solid was added to the beaker and stirred. After the NaOH was completely dissolved, the solution was then transferred to a 250-mL volumetric flask quantitatively. Enough distilled water was added to make the volume about 200-mL. The flask was covered and cooled down to room temperature. The solution was bulked to the mark with distilled water and covered. The solution was mixed by repeated shaking and inversion of the flask. Lastly, the solution was transferred into a dry and clean plastic bottle.

Preparation of 100 mL 3.0 M hydrochloric acid (by dilution)

The volume of 12.1 M HCl solution needed to prepare a 100 mL 3.0 M HCl was calculated (24.8 mL 12.1 M HCl). To obtain the exact amount, pipette was used to measure 24.8 mL of concentrated HCl solution into a 100-mL volumetric flask containing about 25-mL distilled water. Enough distilled water was then added to make the volume about 90-mL. The solution was mixed through swirling and the flask was covered and we let the solution cooled down to room temperature. The solution was bulked to the mark with distilled water and covered then mixed by repeated shaking and inversion of the flask. Lastly, the solution was transferred into a dry and clean plastic bottle.

Standardization of 1.0 M NaOH and 3.0 M HCl solution
For standardization of 1.0M NaOH, three clean and properly labeled 250-mL Erlenmeyer flasks were used and each flask contained 0.1g of the primary standard KHP to the nearest 0.1mg. The weights were recorded. After this, 50 mL of distilled water was added and mixed by swirling to dissolve the solid. 2 to 3 drops of indicator (phenolphthalein) was added and titration was performed with 1.0M NaOH. For the standardization of the HCl solution, we used the same procedure except that 0.1g of Na2CO3 was placed in each of the three Erlenmeyer flask instead of primary standard KHP and 50 mL of boiled distilled water was added and mixed by swirling to dissolve the Na2CO3 solid. We recorded the initial and final burette reading and started titrating.

Tabulated Reported Values

Figure 1. Molar Concentration of Sodium Hydroxide and Hydrochloric Acid and their Percent Deviation Trial| M NaOH| % deviation| M HCl| % deviation|
1| 2.60 M| 160%| 3.12 M| 4%|
2| 3.71 M| 271 %| 3.77 M...
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