1 - VOLUMETRIC SOLUTION AND ACID-BASE TITRATION

• MAKING STANDARD SOLUTION?

  1. Weigh solid in weighing boat to record mass
  2. Transfer solid to beaker
  3. Re-weigh weighing boat and record difference/ rinse into beaker
  4. Add minimum distilled water to beaker to dissolve
  5. Stir beaker using glass rod until solid dissolved
  6. Transfer to 250 cm^3 volumetric flask
  7. Rinse all used glassware into flask
  8. Add distilled water to graduation line
  9. Invert several times
• PURPOSE OF RE-WEIGHING/ RINSING?

  any solid left over is accounted for, gives precise mass
• PURPOSE OF INVERTING?

  fully mixed solution
• ACID BASE TITRATION?

  1. Use glass pipette to transfer x cm^3 acid to conical flask
  2. Add several drops of indicator to conical flask using dropping pipette
  3. Rinse solution on sides of flask into flask with distilled water
  4. Fill burette with base using funnel
  5. Run solution through ensuring no air bubbles present
  6. Remove funnel from burette
  7. Place conical flask on white tile beneath burette
  8. Record starting volume
  9. Titrate solution, swirl conical flask until permanent colour change observed
  10. Record end volume in burette and calculate titre
  11. Repeat until concordant results achieved
  12. Calculate mean titre
• AIR BUBBLE IN BURETTE?

  value of titre is higher than true value
• PURPOSE OF REMOVING FUNNEL?

  droplets from funnel could enter burette and affect titre
• SOURCE OF ERROR WHEN USING BURETTE?

  air bubble in jet
• PURPOSE OF RINSING TO INCREASE TITRE ACCURACY?

  reagent on sides of flask is added to reaction mixture
• WHY DOES RINSING NOT CHANGE VOLUME OF TITRE?

  water not a reagent so does not change number of moles of reagents
• WHY IS A CONICAL FLASK USED?

  less chance of losing liquid on swirling
• PREFERENCE FOR LARGER TITRE BUT NOT TOO LARGE?

  larger, smaller percentage error but too high means refill burette and increase error