PAG 2 - Acid-Base Titration (2.1.4d)

Question 1

How do you prepare a standard solution?

Answer 1

1. Accurately weigh the solid
2. Dissolving the Solute:
   
   1. Add the solute (solid) to a beaker and stir the minimum volume of distilled water with a rod to dissolve it
      
      1. (use distilled water to ensure no impurities are added from tap water)
3. Make up the solution to a known volume
   
   1. _​_A volumetric flask is used as it is more accurate than a measuring cylinder
   2. Transfer the solution in the beaker to the volumetric flask, wash the beaker with distilled water to catch any residue and add this to the flask
   3. Wash the rod to catch any residue and add to the flask
   4. Then make the solution up to the graduated mark
4. Homogenise
   
   1. Place a stopper on top and constantly invert, otherwise the top will be distilled water and the bottom will have the solute

Question 2

Describe the practical procedure for an acid-base titration

Answer 2

1. Add a measured volume (e.g. 25cm³) of one solution to a conical flask (usually a base e.g. NaOH) from a volumetric pipette
2. Add the standard solution of acid to the burette (make a note of the starting volume)
3. Add a few drops of a suitable indicator to the conical flask
4. Run the burette drop by drop until a colour change is seen, this is the end point
5. Record the final burette reading
6. Repeat the titration several times until you get 2 concordant titres (within 0.10cm³ of one another)