Titration Report

By Puan Haslina for WMSKL Form 4 classes, uploaded by LWC 4W Wms4w2010.blogspot.com

Aim / Objective  To determine the end point of neutralization for an acid-base titration and calculate the concentration of acid used.

Problem statement How can the end point and concentration of  acid be determined in acid-base titration by using an indicator?

Hypothesis  The end point of neutralization between ______  acid and ______ hydroxide is reached when the color of phenolphthalein indicator change from pink to colorless.

Fixed variables Volume and concentration of ___________  hydroxide

Manipulated variables

Volume of __________ acid Responding variables End point of titration / color change in phenolphthalein

Material (Total volume ) and concentration of _________  hydroxide, ___________ acid, phenolphthalein indicator

Apparatus 50 cm3 burette, 25 cm3 pipette, 25 cm3 conical flask, retort stand with clamp, pipette pump Procedure 1. Rinse the burette with small volume of acid prepared.

2. Rinse the pipette with small volume of   _________ hydroxide.

3. Clamp the burette to a retort stand and pour the ___________ acid into the burette. Filled the burette with _______ acid and adjust the meniscus level to a reading at zero. The initial burette reading is recorded. 4. 25 cm3 of _________ hydroxide solution is draw up into a pipette and then transferred into a clean conical flask. 5. Place a white tile / paper below the conical flask. 6. Three / Four drops of phenolphthalein are added into the _________  hydroxide. (Observe the color of the solution) 7. The ______ acid is then allowed to run into the conical flask slowly from the burette. The conical flask is swirled throughout the titration. 8. When the colour of the pink solution turns paler, the _______acid is added a

drop at a time at a very slow pace while swirling. 9. The addition of _________ acid is immediately stopped once the solution in the conical flask turns colorless. 10. The final burette reading is recorded. 11. Steps 3 to 9 are repeated three more times and all the readings are tabulated.

Diagram

burette  ________ acid

25 cm3 ________ hydroxide

White tile

Results / Data: (Important note: Burette reading MUST be two decimal points!!!)

 Titration number Initial burette reading (cm3) Final burette reading

1(Roug h data)

2

3

4

(cm3) Volume of ______  acid used (cm3)

Inference:

1. The color of phenopthalein in ________  hydroxide solution is ________  2. End point is reached when the phenolphthalein color changes from ________  to __________  3. From the experiment, 25 cm3 of _____ mol dm-3 __________ hydroxide solution exactly neutralizes _______ cm3 of _________ acid. 4. The chemical equation :  _________________________  5. The ionic equation:  _____________________________ 

Calculation: 1) Average volume of __________ acid used = Volume 2 + 3 + 4 3

= _________ cm3 2) Mol of _________ hydroxide = 1000

MV

3) Find concentration of acid Method 1 Example: NaOH + HCl → NaOH + H2 O From equation: 1 mol NaOH reacts with 1 mol HCl

Method 2 (use formula) MaVa MbVb

= mol a mol b

Discussions / Questions

1. Why do we have to rinse the burette with acid? 2. Why do we have to rinse the pipette with alkali? 3. Why is the conical flask not rinsed with alkali? 3. What is use of the white tile / paper in this activity? 4. If methyl orange is used to replaced phenolphthalein, what is the color change at the end point? Conclusion

 The end point in the titration between ______  acid and ______ hydroxide can be determined using ___________ method.  The concentration of ____________ acid used in this experiment is ________mol dm -3