Exp 2: Acid-Base titration (Discussion)

Why we need to rinse pipette or burette with solution before used it in the experiment? (Choose the best answer)

• to make sure the apparatus is functioning well.

• to remove dirt in the pipette or burette.

• to ensure the concentration of analyte/titrant does not change

• to remove air bubbles in the apparatus

How to ensure the burette reading is accurate?

• Be sure to read the volume at the bottom of the meniscus aligns with graduated mark at eye level

• take measurement more than once and avoid parallax error.

Following is the precautions should be taken during titration except...

• Rinse the tips of the burette upon reach the end point

• if the burette or pipette is not dry before use, it has to be rinsed with the solution that will be transferred.

• The beaker,pipette and the flask should be washed properly with distilled water first

• ensure the burette tap is closed before adding titrant

How to ensure the accurate burette reading is recorded at the end point? (the are more than one correct answer)

• Remove air bubbles at the tip of burette.

• Upon reaching the end pcint, titrate slowly until a pal.e pink colour persist for more than 30 seconds.

• rinse the unreacted solution at the inner wall of conical flask with distilled water.

• Use white tile underneath the conical flask to observe the colour change at end point.

• All is correct

Why we need to remove air bubbles in the burette tip?

• because the presence of air bubbles will affect the volume of titrant used in the titration.

• because the presence of air bubbles will affect the volume of analyte used in the titration.

Determination of the concentration of the solution depends on how accurate the titration values is obtained. How can we achieved this?

• Make sure to take gross reading first.

• repeat titrations at least 3 times.

• Always titrate slowly until pale pink colour appear

• Always start titration at zero mark of burette.

Does addition of water(rinsing) in step 7 (Part B) affect on the accuracy of the titration?

• Yes. because the addition of water will decrease the concentration of acid in conical flask.

• No. because the number of moles of acid react with the base would be same and acid-base reaction depends only on stoichiometric ratio.

It is unnecessary to know exact concentration of oxalic acid to determine the concentration of base. Why?

• because we already know the concentration base in this experiment.

• because the concentration of base does not depends on concentration of oxalic acid.

• because the number of moles taken from the mass of oxalic acid will remain the same in whatever concentration used.