The Aim Of The Experiment Is To Essay Example

these chemicals affects part of your body immediately wash it with water. In order to avoid this, proper safety equipments should be used. You must wear fully buttoned lab coat, goggles and gloves.

2.1 Procedure

1. Take 100 cm3 of 0.100 M solution of sodium hydroxide

2. Prepare a solution with 1.5 g of an unknown acid up to 250 cm3

3. Wash and set up the burette. Fill it with the acid solution

4. Use the pipette to transfer 25.0 cm3 of the 0.100 M sodium hydroxide solution to a 250 cm3 conical flask.

5. Add 3-4 drops of phenol red indicator to the conical flask. Indicator will change its colour from pink in alkaline solution, to yellow in acid solution. When the solution first changes its colour to orange the endpoint is reached. The colour may fade after standing for a few minutes, but this can be ignored.

6. Add the acid from burette until the mixture just goes orange. Use the first titration to obtain an approximate value for the volume of the acid needed.

7. Repeat the titration twice more in order to obtain 3 concordant results. The results are concordant if they are within 0.10 cm3 of each other.

8. Record the results on a table

2.3 Analysis

1. a) Represent unknown acid as HA, and then write an equation for the reaction with sodium hydroxide.

b) Calculate the molarity of a sodium hydroxide solution.

c) The concentration of the acid solution was 1.5 g/250 cm3. Use this value to calculate the relative formula mass of the acid

d) Suggest a possible identity for acid HA which is known to be one of the following:

2. The acid solution was prepared by diluting a standard

solution using a 250 cm3 volumetric flask. Assuming that the maximum errors for the apparatus used in the experiment were:

3. Compare your calculated Mr value with the Mr value of likeliest acid. Calculate

the percentage difference between these two values.

3.1 Implementing

1. Wash all the equipments used in the experiment (including burette, conical flask,

pipette, pipette filler and beaker) with distilled water in the wash bottle.

2. Use pipette to transfer 25 cm3 of sodium hydroxide (alkali) solution into a conical flask.

3. Add 3 or 4 drops of phenol red indicator to the conical flask into which NaOH solution was put.

4. Fill the burette by pipette filler with acid solution up to point 0.00.

5. Take the point at which level of acid solution is least as the initial reading.

Wash the side of conical flask during the titration.

6. Swirl the solution in the conical flask for the indicator to disperse evenly and

continue swirling while adding the acid solution from the burette as well.

7. Start adding acid solution drop wise from the burette carefully to be able to

stop adding acid solution at a correct point when the endpoint is reached.

8. When the purple colour starts to change to yellow, stop adding acid solution. This is the endpoint.

9. Read correctly the final reading of volume on the burette when the endpoint is reached.

10. Repeat the titration two more times in order to obtain more accurate final results.

When repeating the titrations again uses the sodium hydroxide solutions in new conical flask and fills the burette again up to the point 0.00 since the amount of acid solution in one burette is not enough for all 3 titrations.

11. Record the results on a table

3.2

Evaluation

While carrying out this experiment some errors occurred due to the value that was found. From the titration process I found the molarity of the sodium hydroxide solution and the relative formula mass of the unknown acid. With further calculations I identified the correct formula of the acid. The experiment was done without any major mistakes and complications, although there were some minor mistakes in calculations due to the apparatus used. This could be solved in another experiment by using more appropriate equipments. It will reduce the overall percentage error and minimize the mistake.